The perf mmap code is careful about mmap()'ing the user page with the
ringbuffer and additionally the auxiliary buffer, when the event supports
it. Once the first mapping is established, subsequent mapping have to use
the same offset and the same size in both cases. The reference counting for
the ringbuffer and the auxiliary buffer depends on this being correct.
Though perf does not prevent that a related mapping is split via mmap(2),
munmap(2) or mremap(2). A split of a VMA results in perf_mmap_open() calls,
which take reference counts, but then the subsequent perf_mmap_close()
calls are not longer fulfilling the offset and size checks. This leads to
reference count leaks.
As perf already has the requirement for subsequent mappings to match the
initial mapping, the obvious consequence is that VMA splits, caused by
resizing of a mapping or partial unmapping, have to be prevented.
Implement the vm_operations_struct::may_split() callback and return
unconditionally -EINVAL.
That ensures that the mapping offsets and sizes cannot be changed after the
fact. Remapping to a different fixed address with the same size is still
possible as it takes the references for the new mapping and drops those of
the old mapping.
Fixes: 45bfb2e504 ("perf: Add AUX area to ring buffer for raw data streams")
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-27504
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: stable@vger.kernel.org
After successful allocation of a buffer or a successful attachment to an
existing buffer perf_mmap() tries to map the buffer read only into the page
table. If that fails, the already set up page table entries are zapped, but
the other perf specific side effects of that failure are not handled. The
calling code just cleans up the VMA and does not invoke perf_mmap_close().
This leaks reference counts, corrupts user->vm accounting and also results
in an unbalanced invocation of event::event_mapped().
Cure this by moving the event::event_mapped() invocation before the
map_range() call so that on map_range() failure perf_mmap_close() can be
invoked without causing an unbalanced event::event_unmapped() call.
perf_mmap_close() undoes the reference counts and eventually frees buffers.
Fixes: b709eb872e ("perf: map pages in advance")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: stable@vger.kernel.org
When perf_mmap() fails to allocate a buffer, it still invokes the
event_mapped() callback of the related event. On X86 this might increase
the perf_rdpmc_allowed reference counter. But nothing undoes this as
perf_mmap_close() is never called in this case, which causes another
reference count leak.
Return early on failure to prevent that.
Fixes: 1e0fb9ec67 ("perf: Add pmu callbacks to track event mapping and unmapping")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: stable@vger.kernel.org
Failure of the AUX buffer allocation leaks the reference count.
Set the reference count to 1 only when the allocation succeeds.
Fixes: 45bfb2e504 ("perf: Add AUX area to ring buffer for raw data streams")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: stable@vger.kernel.org
A recent overhaul sets the return value to 0 unconditionally after the
allocations, which causes reference count leaks and corrupts the user->vm
accounting.
Preserve the AUX buffer allocation failure return value, so that the
subsequent code works correctly.
Fixes: 0983593f32 ("perf/core: Lift event->mmap_mutex in perf_mmap()")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: stable@vger.kernel.org
Pull non-MM updates from Andrew Morton:
"Significant patch series in this pull request:
- "squashfs: Remove page->mapping references" (Matthew Wilcox) gets
us closer to being able to remove page->mapping
- "relayfs: misc changes" (Jason Xing) does some maintenance and
minor feature addition work in relayfs
- "kdump: crashkernel reservation from CMA" (Jiri Bohac) switches
us from static preallocation of the kdump crashkernel's working
memory over to dynamic allocation. So the difficulty of a-priori
estimation of the second kernel's needs is removed and the first
kernel obtains extra memory
- "generalize panic_print's dump function to be used by other
kernel parts" (Feng Tang) implements some consolidation and
rationalization of the various ways in which a failing kernel
splats information at the operator
* tag 'mm-nonmm-stable-2025-08-03-12-47' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (80 commits)
tools/getdelays: add backward compatibility for taskstats version
kho: add test for kexec handover
delaytop: enhance error logging and add PSI feature description
samples: Kconfig: fix spelling mistake "instancess" -> "instances"
fat: fix too many log in fat_chain_add()
scripts/spelling.txt: add notifer||notifier to spelling.txt
xen/xenbus: fix typo "notifer"
net: mvneta: fix typo "notifer"
drm/xe: fix typo "notifer"
cxl: mce: fix typo "notifer"
KVM: x86: fix typo "notifer"
MAINTAINERS: add maintainers for delaytop
ucount: use atomic_long_try_cmpxchg() in atomic_long_inc_below()
ucount: fix atomic_long_inc_below() argument type
kexec: enable CMA based contiguous allocation
stackdepot: make max number of pools boot-time configurable
lib/xxhash: remove unused functions
init/Kconfig: restore CONFIG_BROKEN help text
lib/raid6: update recov_rvv.c zero page usage
docs: update docs after introducing delaytop
...
Pull MM updates from Andrew Morton:
"As usual, many cleanups. The below blurbiage describes 42 patchsets.
21 of those are partially or fully cleanup work. "cleans up",
"cleanup", "maintainability", "rationalizes", etc.
I never knew the MM code was so dirty.
"mm: ksm: prevent KSM from breaking merging of new VMAs" (Lorenzo Stoakes)
addresses an issue with KSM's PR_SET_MEMORY_MERGE mode: newly
mapped VMAs were not eligible for merging with existing adjacent
VMAs.
"mm/damon: introduce DAMON_STAT for simple and practical access monitoring" (SeongJae Park)
adds a new kernel module which simplifies the setup and usage of
DAMON in production environments.
"stop passing a writeback_control to swap/shmem writeout" (Christoph Hellwig)
is a cleanup to the writeback code which removes a couple of
pointers from struct writeback_control.
"drivers/base/node.c: optimization and cleanups" (Donet Tom)
contains largely uncorrelated cleanups to the NUMA node setup and
management code.
"mm: userfaultfd: assorted fixes and cleanups" (Tal Zussman)
does some maintenance work on the userfaultfd code.
"Readahead tweaks for larger folios" (Ryan Roberts)
implements some tuneups for pagecache readahead when it is reading
into order>0 folios.
"selftests/mm: Tweaks to the cow test" (Mark Brown)
provides some cleanups and consistency improvements to the
selftests code.
"Optimize mremap() for large folios" (Dev Jain)
does that. A 37% reduction in execution time was measured in a
memset+mremap+munmap microbenchmark.
"Remove zero_user()" (Matthew Wilcox)
expunges zero_user() in favor of the more modern memzero_page().
"mm/huge_memory: vmf_insert_folio_*() and vmf_insert_pfn_pud() fixes" (David Hildenbrand)
addresses some warts which David noticed in the huge page code.
These were not known to be causing any issues at this time.
"mm/damon: use alloc_migrate_target() for DAMOS_MIGRATE_{HOT,COLD" (SeongJae Park)
provides some cleanup and consolidation work in DAMON.
"use vm_flags_t consistently" (Lorenzo Stoakes)
uses vm_flags_t in places where we were inappropriately using other
types.
"mm/memfd: Reserve hugetlb folios before allocation" (Vivek Kasireddy)
increases the reliability of large page allocation in the memfd
code.
"mm: Remove pXX_devmap page table bit and pfn_t type" (Alistair Popple)
removes several now-unneeded PFN_* flags.
"mm/damon: decouple sysfs from core" (SeongJae Park)
implememnts some cleanup and maintainability work in the DAMON
sysfs layer.
"madvise cleanup" (Lorenzo Stoakes)
does quite a lot of cleanup/maintenance work in the madvise() code.
"madvise anon_name cleanups" (Vlastimil Babka)
provides additional cleanups on top or Lorenzo's effort.
"Implement numa node notifier" (Oscar Salvador)
creates a standalone notifier for NUMA node memory state changes.
Previously these were lumped under the more general memory
on/offline notifier.
"Make MIGRATE_ISOLATE a standalone bit" (Zi Yan)
cleans up the pageblock isolation code and fixes a potential issue
which doesn't seem to cause any problems in practice.
"selftests/damon: add python and drgn based DAMON sysfs functionality tests" (SeongJae Park)
adds additional drgn- and python-based DAMON selftests which are
more comprehensive than the existing selftest suite.
"Misc rework on hugetlb faulting path" (Oscar Salvador)
fixes a rather obscure deadlock in the hugetlb fault code and
follows that fix with a series of cleanups.
"cma: factor out allocation logic from __cma_declare_contiguous_nid" (Mike Rapoport)
rationalizes and cleans up the highmem-specific code in the CMA
allocator.
"mm/migration: rework movable_ops page migration (part 1)" (David Hildenbrand)
provides cleanups and future-preparedness to the migration code.
"mm/damon: add trace events for auto-tuned monitoring intervals and DAMOS quota" (SeongJae Park)
adds some tracepoints to some DAMON auto-tuning code.
"mm/damon: fix misc bugs in DAMON modules" (SeongJae Park)
does that.
"mm/damon: misc cleanups" (SeongJae Park)
also does what it claims.
"mm: folio_pte_batch() improvements" (David Hildenbrand)
cleans up the large folio PTE batching code.
"mm/damon/vaddr: Allow interleaving in migrate_{hot,cold} actions" (SeongJae Park)
facilitates dynamic alteration of DAMON's inter-node allocation
policy.
"Remove unmap_and_put_page()" (Vishal Moola)
provides a couple of page->folio conversions.
"mm: per-node proactive reclaim" (Davidlohr Bueso)
implements a per-node control of proactive reclaim - beyond the
current memcg-based implementation.
"mm/damon: remove damon_callback" (SeongJae Park)
replaces the damon_callback interface with a more general and
powerful damon_call()+damos_walk() interface.
"mm/mremap: permit mremap() move of multiple VMAs" (Lorenzo Stoakes)
implements a number of mremap cleanups (of course) in preparation
for adding new mremap() functionality: newly permit the remapping
of multiple VMAs when the user is specifying MREMAP_FIXED. It still
excludes some specialized situations where this cannot be performed
reliably.
"drop hugetlb_free_pgd_range()" (Anthony Yznaga)
switches some sparc hugetlb code over to the generic version and
removes the thus-unneeded hugetlb_free_pgd_range().
"mm/damon/sysfs: support periodic and automated stats update" (SeongJae Park)
augments the present userspace-requested update of DAMON sysfs
monitoring files. Automatic update is now provided, along with a
tunable to control the update interval.
"Some randome fixes and cleanups to swapfile" (Kemeng Shi)
does what is claims.
"mm: introduce snapshot_page" (Luiz Capitulino and David Hildenbrand)
provides (and uses) a means by which debug-style functions can grab
a copy of a pageframe and inspect it locklessly without tripping
over the races inherent in operating on the live pageframe
directly.
"use per-vma locks for /proc/pid/maps reads" (Suren Baghdasaryan)
addresses the large contention issues which can be triggered by
reads from that procfs file. Latencies are reduced by more than
half in some situations. The series also introduces several new
selftests for the /proc/pid/maps interface.
"__folio_split() clean up" (Zi Yan)
cleans up __folio_split()!
"Optimize mprotect() for large folios" (Dev Jain)
provides some quite large (>3x) speedups to mprotect() when dealing
with large folios.
"selftests/mm: reuse FORCE_READ to replace "asm volatile("" : "+r" (XXX));" and some cleanup" (wang lian)
does some cleanup work in the selftests code.
"tools/testing: expand mremap testing" (Lorenzo Stoakes)
extends the mremap() selftest in several ways, including adding
more checking of Lorenzo's recently added "permit mremap() move of
multiple VMAs" feature.
"selftests/damon/sysfs.py: test all parameters" (SeongJae Park)
extends the DAMON sysfs interface selftest so that it tests all
possible user-requested parameters. Rather than the present minimal
subset"
* tag 'mm-stable-2025-07-30-15-25' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (370 commits)
MAINTAINERS: add missing headers to mempory policy & migration section
MAINTAINERS: add missing file to cgroup section
MAINTAINERS: add MM MISC section, add missing files to MISC and CORE
MAINTAINERS: add missing zsmalloc file
MAINTAINERS: add missing files to page alloc section
MAINTAINERS: add missing shrinker files
MAINTAINERS: move memremap.[ch] to hotplug section
MAINTAINERS: add missing mm_slot.h file THP section
MAINTAINERS: add missing interval_tree.c to memory mapping section
MAINTAINERS: add missing percpu-internal.h file to per-cpu section
mm/page_alloc: remove trace_mm_alloc_contig_migrate_range_info()
selftests/damon: introduce _common.sh to host shared function
selftests/damon/sysfs.py: test runtime reduction of DAMON parameters
selftests/damon/sysfs.py: test non-default parameters runtime commit
selftests/damon/sysfs.py: generalize DAMON context commit assertion
selftests/damon/sysfs.py: generalize monitoring attributes commit assertion
selftests/damon/sysfs.py: generalize DAMOS schemes commit assertion
selftests/damon/sysfs.py: test DAMOS filters commitment
selftests/damon/sysfs.py: generalize DAMOS scheme commit assertion
selftests/damon/sysfs.py: test DAMOS destinations commitment
...
There's error path that could lead to inactive uprobe:
1) uprobe_register succeeds - updates instruction to int3 and
changes ref_ctr from 0 to 1
2) uprobe_unregister fails - int3 stays in place, but ref_ctr
is changed to 0 (it's not restored to 1 in the fail path)
uprobe is leaked
3) another uprobe_register comes and re-uses the leaked uprobe
and succeds - but int3 is already in place, so ref_ctr update
is skipped and it stays 0 - uprobe CAN NOT be triggered now
4) uprobe_unregister fails because ref_ctr value is unexpected
Fix this by reverting the updated ref_ctr value back to 1 in step 2),
which is the case when uprobe_unregister fails (int3 stays in place), but
we have already updated refctr.
The new scenario will go as follows:
1) uprobe_register succeeds - updates instruction to int3 and
changes ref_ctr from 0 to 1
2) uprobe_unregister fails - int3 stays in place and ref_ctr
is reverted to 1.. uprobe is leaked
3) another uprobe_register comes and re-uses the leaked uprobe
and succeds - but int3 is already in place, so ref_ctr update
is skipped and it stays 1 - uprobe CAN be triggered now
4) uprobe_unregister succeeds
Link: https://lkml.kernel.org/r/20250514101809.2010193-1-jolsa@kernel.org
Fixes: 1cc33161a8 ("uprobes: Support SDT markers having reference count (semaphore)")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Jann reports that uprobes can be used destructively when used in the
middle of an instruction. The kernel only verifies there is a valid
instruction at the requested offset, but due to variable instruction
length cannot determine if this is an instruction as seen by the
intended execution stream.
Additionally, Mark Rutland notes that on architectures that mix data
in the text segment (like arm64), a similar things can be done if the
data word is 'mistaken' for an instruction.
As such, require CAP_SYS_ADMIN for uprobes.
Fixes: c9e0924e5c ("perf/core: open access to probes for CAP_PERFMON privileged process")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/CAG48ez1n4520sq0XrWYDHKiKxE_+WCfAK+qt9qkY4ZiBGmL-5g@mail.gmail.com
If an AUX event overruns, the event core layer intends to disable the
event by setting the 'pending_disable' flag. Unfortunately, the event
is not actually disabled afterwards.
In commit:
ca6c21327c ("perf: Fix missing SIGTRAPs")
the 'pending_disable' flag was changed to a boolean. However, the
AUX event code was not updated accordingly. The flag ends up holding a
CPU number. If this number is zero, the flag is taken as false and the
IRQ work is never triggered.
Later, with commit:
2b84def990 ("perf: Split __perf_pending_irq() out of perf_pending_irq()")
a new IRQ work 'pending_disable_irq' was introduced to handle event
disabling. The AUX event path was not updated to kick off the work queue.
To fix this bug, when an AUX ring buffer overrun is detected, call
perf_event_disable_inatomic() to initiate the pending disable flow.
Also update the outdated comment for setting the flag, to reflect the
boolean values (0 or 1).
Fixes: 2b84def990 ("perf: Split __perf_pending_irq() out of perf_pending_irq()")
Fixes: ca6c21327c ("perf: Fix missing SIGTRAPs")
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: James Clark <james.clark@linaro.org>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Liang Kan <kan.liang@linux.intel.com>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-perf-users@vger.kernel.org
Link: https://lore.kernel.org/r/20250625170737.2918295-1-leo.yan@arm.com
Pull perf fixes from Borislav Petkov:
- Avoid a crash on a heterogeneous machine where not all cores support
the same hw events features
- Avoid a deadlock when throttling events
- Document the perf event states more
- Make sure a number of perf paths switching off or rescheduling events
call perf_cgroup_event_disable()
- Make sure perf does task sampling before its userspace mapping is
torn down, and not after
* tag 'perf_urgent_for_v6.16_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86/intel: Fix crash in icl_update_topdown_event()
perf: Fix the throttle error of some clock events
perf: Add comment to enum perf_event_state
perf/core: Fix WARN in perf_cgroup_switch()
perf: Fix dangling cgroup pointer in cpuctx
perf: Fix cgroup state vs ERROR
perf: Fix sample vs do_exit()
There may be concurrency between perf_cgroup_switch and
perf_cgroup_event_disable. Consider the following scenario: after a new
perf cgroup event is created on CPU0, the new event may not trigger
a reprogramming, causing ctx->is_active to be 0. In this case, when CPU1
disables this perf event, it executes __perf_remove_from_context->
list _del_event->perf_cgroup_event_disable on CPU1, which causes a race
with perf_cgroup_switch running on CPU0.
The following describes the details of this concurrency scenario:
CPU0 CPU1
perf_cgroup_switch:
...
# cpuctx->cgrp is not NULL here
if (READ_ONCE(cpuctx->cgrp) == NULL)
return;
perf_remove_from_context:
...
raw_spin_lock_irq(&ctx->lock);
...
# ctx->is_active == 0 because reprogramm is not
# tigger, so CPU1 can do __perf_remove_from_context
# for CPU0
__perf_remove_from_context:
perf_cgroup_event_disable:
...
if (--ctx->nr_cgroups)
...
# this warning will happened because CPU1 changed
# ctx.nr_cgroups to 0.
WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0);
[peterz: use guard instead of goto unlock]
Fixes: db4a835601 ("perf/core: Set cgroup in CPU contexts for new cgroup events")
Signed-off-by: Luo Gengkun <luogengkun@huaweicloud.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250604033924.3914647-3-luogengkun@huaweicloud.com
Commit a3c3c6667("perf/core: Fix child_total_time_enabled accounting
bug at task exit") moves the event->state update to before
list_del_event(). This makes the event->state test in list_del_event()
always false; never calling perf_cgroup_event_disable().
As a result, cpuctx->cgrp won't be cleared properly; causing havoc.
Fixes: a3c3c6667("perf/core: Fix child_total_time_enabled accounting bug at task exit")
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: David Wang <00107082@163.com>
Link: https://lore.kernel.org/all/aD2TspKH%2F7yvfYoO@e129823.arm.com/
While chasing down a missing perf_cgroup_event_disable() elsewhere,
Leo Yan found that both perf_put_aux_event() and
perf_remove_sibling_event() were also missing one.
Specifically, the rule is that events that switch to OFF,ERROR need to
call perf_cgroup_event_disable().
Unify the disable paths to ensure this.
Fixes: ab43762ef0 ("perf: Allow normal events to output AUX data")
Fixes: 9f0c4fa111 ("perf/core: Add a new PERF_EV_CAP_SIBLING event capability")
Reported-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250605123343.GD35970@noisy.programming.kicks-ass.net
Baisheng Gao reported an ARM64 crash, which Mark decoded as being a
synchronous external abort -- most likely due to trying to access
MMIO in bad ways.
The crash further shows perf trying to do a user stack sample while in
exit_mmap()'s tlb_finish_mmu() -- i.e. while tearing down the address
space it is trying to access.
It turns out that we stop perf after we tear down the userspace mm; a
receipie for disaster, since perf likes to access userspace for
various reasons.
Flip this order by moving up where we stop perf in do_exit().
Additionally, harden PERF_SAMPLE_CALLCHAIN and PERF_SAMPLE_STACK_USER
to abort when the current task does not have an mm (exit_mm() makes
sure to set current->mm = NULL; before commencing with the actual
teardown). Such that CPU wide events don't trip on this same problem.
Fixes: c5ebcedb56 ("perf: Add ability to attach user stack dump to sample")
Reported-by: Baisheng Gao <baisheng.gao@unisoc.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250605110815.GQ39944@noisy.programming.kicks-ass.net
Pull MM updates from Andrew Morton:
- "Add folio_mk_pte()" from Matthew Wilcox simplifies the act of
creating a pte which addresses the first page in a folio and reduces
the amount of plumbing which architecture must implement to provide
this.
- "Misc folio patches for 6.16" from Matthew Wilcox is a shower of
largely unrelated folio infrastructure changes which clean things up
and better prepare us for future work.
- "memory,x86,acpi: hotplug memory alignment advisement" from Gregory
Price adds early-init code to prevent x86 from leaving physical
memory unused when physical address regions are not aligned to memory
block size.
- "mm/compaction: allow more aggressive proactive compaction" from
Michal Clapinski provides some tuning of the (sadly, hard-coded (more
sadly, not auto-tuned)) thresholds for our invokation of proactive
compaction. In a simple test case, the reduction of a guest VM's
memory consumption was dramatic.
- "Minor cleanups and improvements to swap freeing code" from Kemeng
Shi provides some code cleaups and a small efficiency improvement to
this part of our swap handling code.
- "ptrace: introduce PTRACE_SET_SYSCALL_INFO API" from Dmitry Levin
adds the ability for a ptracer to modify syscalls arguments. At this
time we can alter only "system call information that are used by
strace system call tampering, namely, syscall number, syscall
arguments, and syscall return value.
This series should have been incorporated into mm.git's "non-MM"
branch, but I goofed.
- "fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions" from
Andrei Vagin extends the info returned by the PAGEMAP_SCAN ioctl
against /proc/pid/pagemap. This permits CRIU to more efficiently get
at the info about guard regions.
- "Fix parameter passed to page_mapcount_is_type()" from Gavin Shan
implements that fix. No runtime effect is expected because
validate_page_before_insert() happens to fix up this error.
- "kernel/events/uprobes: uprobe_write_opcode() rewrite" from David
Hildenbrand basically brings uprobe text poking into the current
decade. Remove a bunch of hand-rolled implementation in favor of
using more current facilities.
- "mm/ptdump: Drop assumption that pxd_val() is u64" from Anshuman
Khandual provides enhancements and generalizations to the pte dumping
code. This might be needed when 128-bit Page Table Descriptors are
enabled for ARM.
- "Always call constructor for kernel page tables" from Kevin Brodsky
ensures that the ctor/dtor is always called for kernel pgtables, as
it already is for user pgtables.
This permits the addition of more functionality such as "insert hooks
to protect page tables". This change does result in various
architectures performing unnecesary work, but this is fixed up where
it is anticipated to occur.
- "Rust support for mm_struct, vm_area_struct, and mmap" from Alice
Ryhl adds plumbing to permit Rust access to core MM structures.
- "fix incorrectly disallowed anonymous VMA merges" from Lorenzo
Stoakes takes advantage of some VMA merging opportunities which we've
been missing for 15 years.
- "mm/madvise: batch tlb flushes for MADV_DONTNEED and MADV_FREE" from
SeongJae Park optimizes process_madvise()'s TLB flushing.
Instead of flushing each address range in the provided iovec, we
batch the flushing across all the iovec entries. The syscall's cost
was approximately halved with a microbenchmark which was designed to
load this particular operation.
- "Track node vacancy to reduce worst case allocation counts" from
Sidhartha Kumar makes the maple tree smarter about its node
preallocation.
stress-ng mmap performance increased by single-digit percentages and
the amount of unnecessarily preallocated memory was dramaticelly
reduced.
- "mm/gup: Minor fix, cleanup and improvements" from Baoquan He removes
a few unnecessary things which Baoquan noted when reading the code.
- ""Enhance sysfs handling for memory hotplug in weighted interleave"
from Rakie Kim "enhances the weighted interleave policy in the memory
management subsystem by improving sysfs handling, fixing memory
leaks, and introducing dynamic sysfs updates for memory hotplug
support". Fixes things on error paths which we are unlikely to hit.
- "mm/damon: auto-tune DAMOS for NUMA setups including tiered memory"
from SeongJae Park introduces new DAMOS quota goal metrics which
eliminate the manual tuning which is required when utilizing DAMON
for memory tiering.
- "mm/vmalloc.c: code cleanup and improvements" from Baoquan He
provides cleanups and small efficiency improvements which Baoquan
found via code inspection.
- "vmscan: enforce mems_effective during demotion" from Gregory Price
changes reclaim to respect cpuset.mems_effective during demotion when
possible. because presently, reclaim explicitly ignores
cpuset.mems_effective when demoting, which may cause the cpuset
settings to violated.
This is useful for isolating workloads on a multi-tenant system from
certain classes of memory more consistently.
- "Clean up split_huge_pmd_locked() and remove unnecessary folio
pointers" from Gavin Guo provides minor cleanups and efficiency gains
in in the huge page splitting and migrating code.
- "Use kmem_cache for memcg alloc" from Huan Yang creates a slab cache
for `struct mem_cgroup', yielding improved memory utilization.
- "add max arg to swappiness in memory.reclaim and lru_gen" from
Zhongkun He adds a new "max" argument to the "swappiness=" argument
for memory.reclaim MGLRU's lru_gen.
This directs proactive reclaim to reclaim from only anon folios
rather than file-backed folios.
- "kexec: introduce Kexec HandOver (KHO)" from Mike Rapoport is the
first step on the path to permitting the kernel to maintain existing
VMs while replacing the host kernel via file-based kexec. At this
time only memblock's reserve_mem is preserved.
- "mm: Introduce for_each_valid_pfn()" from David Woodhouse provides
and uses a smarter way of looping over a pfn range. By skipping
ranges of invalid pfns.
- "sched/numa: Skip VMA scanning on memory pinned to one NUMA node via
cpuset.mems" from Libo Chen removes a lot of pointless VMA scanning
when a task is pinned a single NUMA mode.
Dramatic performance benefits were seen in some real world cases.
- "JFS: Implement migrate_folio for jfs_metapage_aops" from Shivank
Garg addresses a warning which occurs during memory compaction when
using JFS.
- "move all VMA allocation, freeing and duplication logic to mm" from
Lorenzo Stoakes moves some VMA code from kernel/fork.c into the more
appropriate mm/vma.c.
- "mm, swap: clean up swap cache mapping helper" from Kairui Song
provides code consolidation and cleanups related to the folio_index()
function.
- "mm/gup: Cleanup memfd_pin_folios()" from Vishal Moola does that.
- "memcg: Fix test_memcg_min/low test failures" from Waiman Long
addresses some bogus failures which are being reported by the
test_memcontrol selftest.
- "eliminate mmap() retry merge, add .mmap_prepare hook" from Lorenzo
Stoakes commences the deprecation of file_operations.mmap() in favor
of the new file_operations.mmap_prepare().
The latter is more restrictive and prevents drivers from messing with
things in ways which, amongst other problems, may defeat VMA merging.
- "memcg: decouple memcg and objcg stocks"" from Shakeel Butt decouples
the per-cpu memcg charge cache from the objcg's one.
This is a step along the way to making memcg and objcg charging
NMI-safe, which is a BPF requirement.
- "mm/damon: minor fixups and improvements for code, tests, and
documents" from SeongJae Park is yet another batch of miscellaneous
DAMON changes. Fix and improve minor problems in code, tests and
documents.
- "memcg: make memcg stats irq safe" from Shakeel Butt converts memcg
stats to be irq safe. Another step along the way to making memcg
charging and stats updates NMI-safe, a BPF requirement.
- "Let unmap_hugepage_range() and several related functions take folio
instead of page" from Fan Ni provides folio conversions in the
hugetlb code.
* tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (285 commits)
mm: pcp: increase pcp->free_count threshold to trigger free_high
mm/hugetlb: convert use of struct page to folio in __unmap_hugepage_range()
mm/hugetlb: refactor __unmap_hugepage_range() to take folio instead of page
mm/hugetlb: refactor unmap_hugepage_range() to take folio instead of page
mm/hugetlb: pass folio instead of page to unmap_ref_private()
memcg: objcg stock trylock without irq disabling
memcg: no stock lock for cpu hot-unplug
memcg: make __mod_memcg_lruvec_state re-entrant safe against irqs
memcg: make count_memcg_events re-entrant safe against irqs
memcg: make mod_memcg_state re-entrant safe against irqs
memcg: move preempt disable to callers of memcg_rstat_updated
memcg: memcg_rstat_updated re-entrant safe against irqs
mm: khugepaged: decouple SHMEM and file folios' collapse
selftests/eventfd: correct test name and improve messages
alloc_tag: check mem_profiling_support in alloc_tag_init
Docs/damon: update titles and brief introductions to explain DAMOS
selftests/damon/_damon_sysfs: read tried regions directories in order
mm/damon/tests/core-kunit: add a test for damos_set_filters_default_reject()
mm/damon/paddr: remove unused variable, folio_list, in damon_pa_stat()
mm/damon/sysfs-schemes: fix wrong comment on damons_sysfs_quota_goal_metric_strs
...
The PERF_RECORD_THROTTLE records are dumped for all throttled events.
It's not necessary for group events, which are throttled altogether.
Optimize it by only dump the throttle log for the leader.
The sample right after the THROTTLE record must be generated by the
actual target event. It is good enough for the perf tool to locate the
actual target event.
Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20250520181644.2673067-3-kan.liang@linux.intel.com
The current throttle logic doesn't work well with a group, e.g., the
following sampling-read case.
$ perf record -e "{cycles,cycles}:S" ...
$ perf report -D | grep THROTTLE | tail -2
THROTTLE events: 426 ( 9.0%)
UNTHROTTLE events: 425 ( 9.0%)
$ perf report -D | grep PERF_RECORD_SAMPLE -a4 | tail -n 5
0 1020120874009167 0x74970 [0x68]: PERF_RECORD_SAMPLE(IP, 0x1):
... sample_read:
.... group nr 2
..... id 0000000000000327, value 000000000cbb993a, lost 0
..... id 0000000000000328, value 00000002211c26df, lost 0
The second cycles event has a much larger value than the first cycles
event in the same group.
The current throttle logic in the generic code only logs the THROTTLE
event. It relies on the specific driver implementation to disable
events. For all ARCHs, the implementation is similar. Only the event is
disabled, rather than the group.
The logic to disable the group should be generic for all ARCHs. Add the
logic in the generic code. The following patch will remove the buggy
driver-specific implementation.
The throttle only happens when an event is overflowed. Stop the entire
group when any event in the group triggers the throttle.
The MAX_INTERRUPTS is set to all throttle events.
The unthrottled could happen in 3 places.
- event/group sched. All events in the group are scheduled one by one.
All of them will be unthrottled eventually. Nothing needs to be
changed.
- The perf_adjust_freq_unthr_events for each tick. Needs to restart the
group altogether.
- The __perf_event_period(). The whole group needs to be restarted
altogether as well.
With the fix,
$ sudo perf report -D | grep PERF_RECORD_SAMPLE -a4 | tail -n 5
0 3573470770332 0x12f5f8 [0x70]: PERF_RECORD_SAMPLE(IP, 0x2):
... sample_read:
.... group nr 2
..... id 0000000000000a28, value 00000004fd3dfd8f, lost 0
..... id 0000000000000a29, value 00000004fd3dfd8f, lost 0
Suggested-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20250520181644.2673067-2-kan.liang@linux.intel.com
perf always allocates contiguous AUX pages based on aux_watermark.
However, this contiguous allocation doesn't benefit all PMUs. For
instance, ARM SPE and TRBE operate with virtual pages, and Coresight
ETR allocates a separate buffer. For these PMUs, allocating contiguous
AUX pages unnecessarily exacerbates memory fragmentation. This
fragmentation can prevent their use on long-running devices.
This patch modifies the perf driver to be memory-friendly by default,
by allocating non-contiguous AUX pages. For PMUs requiring contiguous
pages (Intel BTS and some Intel PT), the existing
PERF_PMU_CAP_AUX_NO_SG capability can be used. For PMUs that don't
require but can benefit from contiguous pages (some Intel PT), a new
capability, PERF_PMU_CAP_AUX_PREFER_LARGE, is added to maintain their
existing behavior.
Signed-off-by: Yabin Cui <yabinc@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: James Clark <james.clark@linaro.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20250508232642.148767-1-yabinc@google.com
uprobe_write_opcode() does some pretty low-level things that really, it
shouldn't be doing: for example, manually breaking COW by allocating
anonymous folios and replacing mapped pages.
Further, it does seem to do some shaky things: for example, writing to
possible COW-shared anonymous pages or zapping anonymous pages that might
be pinned. We're also not taking care of uffd, uffd-wp, softdirty ...
although rather corner cases here. Let's just get it right like ordinary
ptrace writes would.
Let's rewrite the code, leaving COW-breaking to core-MM, triggered by
FOLL_FORCE|FOLL_WRITE (note that the code was already using FOLL_FORCE).
We'll use GUP to lookup/faultin the page and break COW if required. Then,
we'll walk the page tables using a folio_walk to perform our page
modification atomically by temporarily unmap the PTE + flushing the TLB.
Likely, we could avoid the temporary unmap in case we can just atomically
write the instruction, but that will be a separate project.
Unfortunately, we still have to implement the zapping logic manually,
because we only want to zap in specific circumstances (e.g., page content
identical).
Note that we can now handle large folios (compound pages) and the shared
zeropage just fine, so drop these checks.
Link: https://lkml.kernel.org/r/20250321113713.204682-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Namhyung kim <namhyung@kernel.org>
Cc: Russel King <linux@armlinux.org.uk>
Cc: tongtiangen <tongtiangen@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "kernel/events/uprobes: uprobe_write_opcode() rewrite", v3.
Currently, uprobe_write_opcode() implements COW-breaking manually, which
is really far from ideal. Further, there is interest in supporting
uprobes on hugetlb pages [1], and leaving at least the COW-breaking to the
core will make this much easier.
Also, I think the current code doesn't really handle some things properly
(see patch #3) when replacing/zapping pages.
Let's rewrite it, to leave COW-breaking to the fault handler, and handle
registration/unregistration by temporarily unmapping the anonymous page,
modifying it, and mapping it again. We still have to implement zapping of
anonymous pages ourselves, unfortunately.
We could look into not performing the temporary unmapping if we can
perform the write atomically, which would likely also make adding hugetlb
support a lot easier. But, limited (e.g., only PMD/PUD) hugetlb support
could be added on top of this with some tweaking.
Note that we now won't have to allocate another anonymous folio when
unregistering (which will be beneficial for hugetlb as well), we can
simply modify the already-mapped one from the registration (if any). When
registering a uprobe, we'll first trigger a ptrace-like write fault to
break COW, to then modify the already-mapped page.
Briefly sanity tested with perf probes and with the bpf uprobes selftest.
This patch (of 3):
Pass VMA instead of MM to remove_breakpoint() and remove the "MM" argument
from install_breakpoint(), because it can easily be derived from the VMA.
Link: https://lkml.kernel.org/r/20250321113713.204682-1-david@redhat.com
Link: https://lkml.kernel.org/r/20250321113713.204682-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Namhyung kim <namhyung@kernel.org>
Cc: Russel King <linux@armlinux.org.uk>
Cc: tongtiangen <tongtiangen@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
While an event tears down all links to it as an aux, the iteration
happens on the event's group leader instead of the group itself.
If the event is a group leader, it has no effect because the event is
also its own group leader. But otherwise there would be a risk to detach
all the siblings events from the wrong group leader.
It just happens to work because each sibling's aux link is tested
against the right event before proceeding. Also the ctx lock is the same
for the events and their group leader so the iteration is safe.
Yet the iteration is confusing. Clarify the actual intent.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250424161128.29176-5-frederic@kernel.org
The following commit:
da916e96e2 ("perf: Make perf_pmu_unregister() useable")
has introduced two significant event's parent lifecycle changes:
1) An event that has exited now has EVENT_TOMBSTONE as a parent.
This can result in a situation where the delayed wakeup irq_work can
accidentally dereference EVENT_TOMBSTONE on:
CPU 0 CPU 1
----- -----
__schedule()
local_irq_disable()
rq_lock()
<NMI>
perf_event_overflow()
irq_work_queue(&child->pending_irq)
</NMI>
perf_event_task_sched_out()
raw_spin_lock(&ctx->lock)
ctx_sched_out()
ctx->is_active = 0
event_sched_out(child)
raw_spin_unlock(&ctx->lock)
perf_event_release_kernel(parent)
perf_remove_from_context(child)
raw_spin_lock_irq(&ctx->lock)
// Sees !ctx->is_active
// Removes from context inline
__perf_remove_from_context(child)
perf_child_detach(child)
event->parent = EVENT_TOMBSTONE
raw_spin_rq_unlock_irq(rq);
<IRQ>
perf_pending_irq()
perf_event_wakeup(child)
ring_buffer_wakeup(child)
rcu_dereference(child->parent->rb) <--- CRASH
This also concerns the call to kill_fasync() on parent->fasync.
2) The final parent reference count decrement can now happen before the
the final child reference count decrement. ie: the parent can now
be freed before its child. On PREEMPT_RT, this can result in a
situation where the delayed wakeup irq_work can accidentally
dereference a freed parent:
CPU 0 CPU 1 CPU 2
----- ----- ------
perf_pmu_unregister()
pmu_detach_events()
pmu_get_event()
atomic_long_inc_not_zero(&child->refcount)
<NMI>
perf_event_overflow()
irq_work_queue(&child->pending_irq);
</NMI>
<IRQ>
irq_work_run()
wake_irq_workd()
</IRQ>
preempt_schedule_irq()
=========> SWITCH to workd
irq_work_run_list()
perf_pending_irq()
perf_event_wakeup(child)
ring_buffer_wakeup(child)
event = child->parent
perf_event_release_kernel(parent)
// Not last ref, PMU holds it
put_event(child)
// Last ref
put_event(parent)
free_event()
call_rcu(...)
rcu_core()
free_event_rcu()
rcu_dereference(event->rb) <--- CRASH
This also concerns the call to kill_fasync() on parent->fasync.
The "easy" solution to 1) is to check that event->parent is not
EVENT_TOMBSTONE on perf_event_wakeup() (including both ring buffer
and fasync uses).
The "easy" solution to 2) is to turn perf_event_wakeup() to wholefully
run under rcu_read_lock().
However because of 2), sanity would prescribe to make event::parent
an __rcu pointer and annotate each and every users to prove they are
reliable.
Propose an alternate solution and restore the stable pointer to the
parent until all its children have called _free_event() themselves to
avoid any further accident. Also revert the EVENT_TOMBSTONE design
that is mostly here to determine which caller of perf_event_exit_event()
must perform the refcount decrement on a child event matching the
increment in inherit_event().
Arrange instead for checking the attach state of an event prior to its
removal and decrement the refcount of the child accordingly.
Fixes: da916e96e2 ("perf: Make perf_pmu_unregister() useable")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
When inherit_event() fails after the child allocation but before the
parent refcount has been incremented, calling put_event() wrongly
decrements the reference to the parent, risking to free it too early.
Also pmu_get_event() can't be holding a reference to the child
concurrently at this point since it is under pmus_srcu critical section.
Fix it with restoring the deleted free_event() function and call it on
the failing child in order to free it directly under the verified
assumption that its refcount is only 1. The refcount to the parent is
then voluntarily omitted.
Fixes: da916e96e2 ("perf: Make perf_pmu_unregister() useable")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250424161128.29176-2-frederic@kernel.org
According to the throttling mechanism, the pmu interrupts number can not
exceed the max_samples_per_tick in one tick. But this mechanism is
ineffective when max_samples_per_tick=1, because the throttling check is
skipped during the first interrupt and only performed when the second
interrupt arrives.
Perhaps this bug may cause little influence in one tick, but if in a
larger time scale, the problem can not be underestimated.
When max_samples_per_tick = 1:
Allowed-interrupts-per-second max-samples-per-second default-HZ ARCH
200 100 100 X86
500 250 250 ARM64
...
Obviously, the pmu interrupt number far exceed the user's expect.
Fixes: e050e3f0a7 ("perf: Fix broken interrupt rate throttling")
Signed-off-by: Qing Wang <wangqing7171@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250405141635.243786-3-wangqing7171@gmail.com
So there are three situations:
* If perf_event_free_task() has removed all the children from the parent list
before perf_event_release_kernel() got a chance to even iterate them, then
it's all good as there is no get_ctx() pending.
* If perf_event_release_kernel() iterates a child event, but it gets freed
meanwhile by perf_event_free_task() while the mutexes are temporarily
unlocked, it's all good because while locking again the ctx mutex,
perf_event_release_kernel() observes TASK_TOMBSTONE.
* But if perf_event_release_kernel() frees the child event before
perf_event_free_task() got a chance, we may face this scenario:
perf_event_release_kernel() perf_event_free_task()
-------------------------- ------------------------
mutex_lock(&event->child_mutex)
get_ctx(child->ctx)
mutex_unlock(&event->child_mutex)
mutex_lock(ctx->mutex)
mutex_lock(&event->child_mutex)
perf_remove_from_context(child)
mutex_unlock(&event->child_mutex)
mutex_unlock(ctx->mutex)
// This lock acquires ctx->refcount == 2
// visibility
mutex_lock(ctx->mutex)
ctx->task = TASK_TOMBSTONE
mutex_unlock(ctx->mutex)
wait_var_event()
// enters prepare_to_wait() since
// ctx->refcount == 2
// is guaranteed to be seen
set_current_state(TASK_INTERRUPTIBLE)
smp_mb()
if (ctx->refcount != 1)
schedule()
put_ctx()
// NOT fully ordered! Only RELEASE semantics
refcount_dec_and_test()
atomic_fetch_sub_release()
// So TASK_TOMBSTONE is not guaranteed to be seen
if (ctx->task == TASK_TOMBSTONE)
wake_up_var()
Basically it's a broken store buffer:
perf_event_release_kernel() perf_event_free_task()
-------------------------- ------------------------
ctx->task = TASK_TOMBSTONE smp_store_release(&ctx->refcount, ctx->refcount - 1)
smp_mb()
READ_ONCE(ctx->refcount) READ_ONCE(ctx->task)
So we need a smp_mb__after_atomic() before looking at ctx->task.
Fixes: 59f3aa4a3e ("perf: Simplify perf_event_free_task() wait")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/Z_ZvmEhjkAhplCBE@localhost.localdomain
Previously it was only safe to call perf_pmu_unregister() if there
were no active events of that pmu around -- which was impossible to
guarantee since it races all sorts against perf_init_event().
Rework the whole thing by:
- keeping track of all events for a given pmu
- 'hiding' the pmu from perf_init_event()
- waiting for the appropriate (s)rcu grace periods such that all
prior references to the PMU will be completed
- detaching all still existing events of that pmu (see first point)
and moving them to a new REVOKED state.
- actually freeing the pmu data.
Where notably the new REVOKED state must inhibit all event actions
from reaching code that wants to use event->pmu.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lkml.kernel.org/r/20250307193723.525402029@infradead.org
The task passed to perf_event_exit_task() is not a child, it is
current. Fix this confusing naming, since much of the rest of the code
also relies on it being current.
Specifically, both exec() and exit() callers use it with current as
the argument.
Notably, task_ctx_sched_out() doesn't make much sense outside of
current.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lkml.kernel.org/r/20250307193305.486326750@infradead.org
Currently perf_event_release_kernel() will iterate the child events and attempt
tear-down. However, it removes them from the child_list using list_move(),
notably skipping the state management done by perf_child_detach().
Crucially, it fails to clear PERF_ATTACH_CHILD, which opens the door for a
concurrent perf_remove_from_context() to race.
This way child_list management stays fully serialized using child_mutex.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lkml.kernel.org/r/20250307193305.486326750@infradead.org
Perf can hang while freeing a sigtrap event if a related deferred
signal hadn't managed to be sent before the file got closed:
perf_event_overflow()
task_work_add(perf_pending_task)
fput()
task_work_add(____fput())
task_work_run()
____fput()
perf_release()
perf_event_release_kernel()
_free_event()
perf_pending_task_sync()
task_work_cancel() -> FAILED
rcuwait_wait_event()
Once task_work_run() is running, the list of pending callbacks is
removed from the task_struct and from this point on task_work_cancel()
can't remove any pending and not yet started work items, hence the
task_work_cancel() failure and the hang on rcuwait_wait_event().
Task work could be changed to remove one work at a time, so a work
running on the current task can always cancel a pending one, however
the wait / wake design is still subject to inverted dependencies when
remote targets are involved, as pictured by Oleg:
T1 T2
fd = perf_event_open(pid => T2->pid); fd = perf_event_open(pid => T1->pid);
close(fd) close(fd)
<IRQ> <IRQ>
perf_event_overflow() perf_event_overflow()
task_work_add(perf_pending_task) task_work_add(perf_pending_task)
</IRQ> </IRQ>
fput() fput()
task_work_add(____fput()) task_work_add(____fput())
task_work_run() task_work_run()
____fput() ____fput()
perf_release() perf_release()
perf_event_release_kernel() perf_event_release_kernel()
_free_event() _free_event()
perf_pending_task_sync() perf_pending_task_sync()
rcuwait_wait_event() rcuwait_wait_event()
Therefore the only option left is to acquire the event reference count
upon queueing the perf task work and release it from the task work, just
like it was done before 3a5465418f ("perf: Fix event leak upon exec and file release")
but without the leaks it fixed.
Some adjustments are necessary to make it work:
* A child event might dereference its parent upon freeing. Care must be
taken to release the parent last.
* Some places assuming the event doesn't have any reference held and
therefore can be freed right away must instead put the reference and
let the reference counting to its job.
Reported-by: "Yi Lai" <yi1.lai@linux.intel.com>
Closes: https://lore.kernel.org/all/Zx9Losv4YcJowaP%2F@ly-workstation/
Reported-by: syzbot+3c4321e10eea460eb606@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/673adf75.050a0220.87769.0024.GAE@google.com/
Fixes: 3a5465418f ("perf: Fix event leak upon exec and file release")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250304135446.18905-1-frederic@kernel.org
Avoid a false-positive lockdep warning in the CONFIG_PREEMPT_RT=y
configuration when using write_seqcount_begin() in the uprobe timer
callback by using raw_write_* APIs.
Uprobe's use of timer callback is guaranteed to not race with itself
for a given uprobe_task, and as such seqcount's insistence on having
preemption disabled on the writer side is irrelevant. So switch to
raw_ variants of seqcount API instead of disabling preemption unnecessarily.
Also, point out in the comments more explicitly why we use seqcount
despite our reader side being rather simple and never retrying. We favor
well-maintained kernel primitive in favor of open-coding our own memory
barriers.
Fixes: 8622e45b5d ("uprobes: Reuse return_instances between multiple uretprobes within task")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Suggested-by: Sebastian Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20250404194848.2109539-1-andrii@kernel.org
Move the get_ctx(child_ctx) call and the child_event->ctx assignment to
occur immediately after the child event is allocated. Ensure that
child_event->ctx is non-NULL before any subsequent error path within
inherit_event calls free_event(), satisfying the assumptions of the
cleanup code.
Details:
There's no clear Fixes tag, because this bug is a side-effect of
multiple interacting commits over time (up to 15 years old), not
a single regression.
The code initially incremented refcount then assigned context
immediately after the child_event was created. Later, an early
validity check for child_event was added before the
refcount/assignment. Even later, a WARN_ON_ONCE() cleanup check was
added, assuming event->ctx is valid if the pmu_ctx is valid.
The problem is that the WARN_ON_ONCE() could trigger after the initial
check passed but before child_event->ctx was assigned, violating its
precondition. The solution is to assign child_event->ctx right after
its initial validation. This ensures the context exists for any
subsequent checks or cleanup routines, resolving the WARN_ON_ONCE().
To resolve it, defer the refcount update and child_event->ctx assignment
directly after child_event->pmu_ctx is set but before checking if the
parent event is orphaned. The cleanup routine depends on
event->pmu_ctx being non-NULL before it verifies event->ctx is
non-NULL. This also maintains the author's original intent of passing
in child_ctx to find_get_pmu_context before its refcount/assignment.
[ mingo: Expanded the changelog from another email by Gabriel Shahrouzi. ]
Reported-by: syzbot+ff3aa851d46ab82953a3@syzkaller.appspotmail.com
Signed-off-by: Gabriel Shahrouzi <gshahrouzi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Link: https://lore.kernel.org/r/20250405203036.582721-1-gshahrouzi@gmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ff3aa851d46ab82953a3
Pull perf event fix from Ingo Molnar:
"Fix a perf events time accounting bug"
* tag 'perf-urgent-2025-04-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/core: Fix child_total_time_enabled accounting bug at task exit
