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

Summary

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.

Timeline

1. Apr 13, 2026, 1:40 PM UTCCVE published
2. Oct 15, 2026, 1:16 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in ad8e8fec40290a8c8cf145c0deaadf76f80c5163; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in ab1ff5890c7354afc7be56502fcfbd61f3b7ae4f; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 25b6821884713a31e2b49fb67b0ebd765b33e0a9; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in c56f78614e7781aaceca9bd3cb2128bf7d45c3bd; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in b9e6431cbea8bb1fae8069ed099b4ee100499835; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 17c1b9807b8a67d676b6dcf749ee932ebaa7f568; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in d0aefec1b1a1ba2c1d251028dc2c4e5b4ce1fea5; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 4576100b8cd03118267513cafacde164b498b322

• Linux Linux

  2.6.12

• KernelLinux

  From 2.6.12 · fixed in 5.10.253; From 5.11.0 · fixed in 5.15.203; From 5.16.0 · fixed in 6.1.168; From 6.2.0 · fixed in 6.6.134; From 6.7.0 · fixed in 6.12.81; From 6.13.0 · fixed in 6.18.22; From 6.19.0 · fixed in 6.19.12

References 8