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95f1c1e98d
I have seen syzbot reports hinting at xt_hashlimit abuse: [ 105.783066][ T4331] xt_hashlimit: max too large, truncated to 1048576 [ 105.811405][ T4331] xt_hashlimit: size too large, truncated to 1048576 And worker threads using up to 1 second per htable_selective_cleanup() invocation. [ 269.734496][ C1] [<ffffffff81547180>] ? __local_bh_enable_ip+0x1a0/0x1a0 [ 269.734513][ C1] [<ffffffff817d75d0>] ? lockdep_hardirqs_on_prepare+0x740/0x740 [ 269.734533][ C1] [<ffffffff852e71ff>] ? htable_selective_cleanup+0x25f/0x310 [ 269.734549][ C1] [<ffffffff817dcd30>] ? __lock_acquire+0x2060/0x2060 [ 269.734567][ C1] [<ffffffff817f058a>] ? do_raw_spin_lock+0x14a/0x370 [ 269.734583][ C1] [<ffffffff852e71ff>] ? htable_selective_cleanup+0x25f/0x310 [ 269.734599][ C1] [<ffffffff81547147>] __local_bh_enable_ip+0x167/0x1a0 [ 269.734616][ C1] [<ffffffff81546fe0>] ? _local_bh_enable+0xa0/0xa0 [ 269.734634][ C1] [<ffffffff852e71ff>] ? htable_selective_cleanup+0x25f/0x310 [ 269.734651][ C1] [<ffffffff852e71ff>] htable_selective_cleanup+0x25f/0x310 [ 269.734670][ C1] [<ffffffff815b3cc9>] ? process_one_work+0x7a9/0x1170 [ 269.734685][ C1] [<ffffffff852e57db>] htable_gc+0x1b/0xa0 [ 269.734700][ C1] [<ffffffff815b3cc9>] ? process_one_work+0x7a9/0x1170 [ 269.734714][ C1] [<ffffffff815b3dc9>] process_one_work+0x8a9/0x1170 [ 269.734733][ C1] [<ffffffff815b3520>] ? worker_detach_from_pool+0x260/0x260 [ 269.734749][ C1] [<ffffffff810201c7>] ? _raw_spin_lock_irq+0xb7/0xf0 [ 269.734763][ C1] [<ffffffff81020110>] ? _raw_spin_lock_irqsave+0x100/0x100 [ 269.734777][ C1] [<ffffffff8159d3df>] ? wq_worker_sleeping+0x5f/0x270 [ 269.734800][ C1] [<ffffffff815b53c7>] worker_thread+0xa47/0x1200 [ 269.734815][ C1] [<ffffffff81020010>] ? _raw_spin_lock+0x40/0x40 [ 269.734835][ C1] [<ffffffff815c9f2a>] kthread+0x25a/0x2e0 [ 269.734853][ C1] [<ffffffff815b4980>] ? worker_clr_flags+0x190/0x190 [ 269.734866][ C1] [<ffffffff815c9cd0>] ? kthread_blkcg+0xd0/0xd0 [ 269.734885][ C1] [<ffffffff81027b1a>] ret_from_fork+0x3a/0x50 We can skip over empty buckets, avoiding the lockdep penalty for debug kernels, and avoid atomic operations on non debug ones. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.