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CVE-2026-31423 net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()

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.

Affected products and versions

Product Affected versions Fixed in
Linux 7.0 earliest → < 7.0 7.0
Linux 6.19 earliest → < 6.19.12 6.19.12
Linux 6.18 earliest → < 6.18.22 6.18.22
Linux 6.12 earliest → < 6.12.81 6.12.81
Linux 6.6 earliest → < 6.6.134 6.6.134
Linux 6.1 earliest → < 6.1.168 6.1.168
Linux 5.15 earliest → < 5.15.203 5.15.203
Linux 5.10 earliest → < 5.10.253 5.10.253
Linux 2.6.12 No fix stated
Show the 3 other branches
Product Affected versions Fixed in
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated

References

Timeline

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