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744a56389f
strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.
in file.c:
s_last_mounted is marked as __nonstring meaning it does not need to be
NUL-terminated. Let's instead use strtomem_pad() to copy bytes from the
string source to the byte array destination -- while also ensuring to
pad with zeroes.
in ioctl.c:
We can drop the memset and size argument in favor of using the new
2-argument version of strscpy_pad() -- which was introduced with Commit
e6584c3964 ("string: Allow 2-argument strscpy()"). This guarantees
NUL-termination and NUL-padding on the destination buffer -- which seems
to be a requirement judging from this comment:
| static int ext4_ioctl_getlabel(struct ext4_sb_info *sbi, char __user *user_label)
| {
| char label[EXT4_LABEL_MAX + 1];
|
| /*
| * EXT4_LABEL_MAX must always be smaller than FSLABEL_MAX because
| * FSLABEL_MAX must include terminating null byte, while s_volume_name
| * does not have to.
| */
in super.c:
s_first_error_func is marked as __nonstring meaning we can take the same
approach as in file.c; just use strtomem_pad()
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240321-strncpy-fs-ext4-file-c-v1-1-36a6a09fef0c@google.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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.