CVE-2024-26720: mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again

In the Linux kernel, the following vulnerability has been resolved: mm/writeback: fix possible divide-by-zero in wbdirtylimits(), again (struct dirtythrottlecontrol )->thresh is an unsigned long, but is passed as the u32 divisor argument to divu64(). On architectures where unsigned long is 64 bytes, the argument will be implicitly truncated. Use div64u64() instead of divu64() 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 domaindritylimits() uses, but is much easier in global writeback domain with a BDICAPSTRICTLIMIT-backing device, using e.g. vm.dirtybytes=(1<<32)PAGESIZE so that dtc->thresh == (1<<32)

— Launchpad

Rejected reason: This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.

— NVD