04ffde1319
While there is logic about the difference between ksize and usize,
copy_struct_from_user() didn't check the size of the destination buffer
(when it was known) against ksize. Add this check so there is an upper
bounds check on the possible memset() call, otherwise lower bounds
checks made by callers will trigger bounds warnings under -Warray-bounds.
Seen under GCC 13:
In function 'copy_struct_from_user',
inlined from 'iommufd_fops_ioctl' at
../drivers/iommu/iommufd/main.c:333:8:
../include/linux/fortify-string.h:59:33: warning: '__builtin_memset' offset [57, 4294967294] is out of the bounds [0, 56] of object 'buf' with type 'union ucmd_buffer' [-Warray-bounds=]
59 | #define __underlying_memset __builtin_memset
| ^
../include/linux/fortify-string.h:453:9: note: in expansion of macro '__underlying_memset'
453 | __underlying_memset(p, c, __fortify_size); \
| ^~~~~~~~~~~~~~~~~~~
../include/linux/fortify-string.h:461:25: note: in expansion of macro '__fortify_memset_chk'
461 | #define memset(p, c, s) __fortify_memset_chk(p, c, s, \
| ^~~~~~~~~~~~~~~~~~~~
../include/linux/uaccess.h:334:17: note: in expansion of macro 'memset'
334 | memset(dst + size, 0, rest);
| ^~~~~~
../drivers/iommu/iommufd/main.c: In function 'iommufd_fops_ioctl':
../drivers/iommu/iommufd/main.c:311:27: note: 'buf' declared here
311 | union ucmd_buffer buf;
| ^~~
Cc: Christian Brauner <brauner@kernel.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Alexander Potapenko <glider@google.com>
Acked-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/lkml/20230203193523.never.667-kees@kernel.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 Restructured Text 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.