CVE-2026-31423

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_hfsc: fix divide-by-zero in rtsc_min() m2sm() converts a u32 slope to a u64 scaled value. For large inputs (e.g. m1=4000000000), the result can reach 2^32. rtsc_min() stores the difference of two such u64 values in a u32 variable `dsm` and uses it as a divisor. When the difference is exactly 2^32 the truncation yields zero, causing a divide-by-zero oops in the concave-curve intersection path: Oops: divide error: 0000 RIP: 0010:rtsc_min (net/sched/sch_hfsc.c:601) Call Trace: init_ed (net/sched/sch_hfsc.c:629) hfsc_enqueue (net/sched/sch_hfsc.c:1569) [...] Widen `dsm` to u64 and replace do_div() with div64_u64() so the full difference is preserved.

References

• https://git.kernel.org/stable/c/17c1b9807b8a67d676b6dcf749ee932ebaa7f568
• https://git.kernel.org/stable/c/25b6821884713a31e2b49fb67b0ebd765b33e0a9
• https://git.kernel.org/stable/c/4576100b8cd03118267513cafacde164b498b322
• https://git.kernel.org/stable/c/b9e6431cbea8bb1fae8069ed099b4ee100499835
• https://git.kernel.org/stable/c/c56f78614e7781aaceca9bd3cb2128bf7d45c3bd