ec18ec2303
commit 9319b647902cbd5cc884ac08a8a6d54ce111fc78 upstream. (struct dirty_throttle_control *)->thresh is an unsigned long, but is passed as the u32 divisor argument to div_u64(). On architectures where unsigned long is 64 bytes, the argument will be implicitly truncated. Use div64_u64() instead of div_u64() so that the value used in the "is this a safe division" check is the same as the divisor. Also, remove redundant cast of the numerator to u64, as that should happen implicitly. This would be difficult to exploit in memcg domain, given the ratio-based arithmetic domain_drity_limits() uses, but is much easier in global writeback domain with a BDI_CAP_STRICTLIMIT-backing device, using e.g. vm.dirty_bytes=(1<<32)*PAGE_SIZE so that dtc->thresh == (1<<32) Link: https://lkml.kernel.org/r/20240118181954.1415197-1-zokeefe@google.com Fixes: f6789593d5ce ("mm/page-writeback.c: fix divide by zero in bdi_dirty_limits()") Signed-off-by: Zach O'Keefe <zokeefe@google.com> Cc: Maxim Patlasov <MPatlasov@parallels.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.