← Back to CVE List
CVE-2026-90072NVD
Vulnerability Summary
In the Linux kernel, the following vulnerability has been resolved:
net/sched: sfq: clamp quantum to avoid signed overflow soft lockup
sfq_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) (unsigned). A
device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU
2147483634) makes psched_mtu() return 0x80000000, so slot->allot = INT_MIN
and INT_MIN + INT_MIN toggles between INT_MIN and 0 forever, spinning
sfq_dequeue() under the qdisc lock.
Clamp the quantum to [256, 1 << 20] so the refill loop terminates. The
lower bound also covers q->quantum == 0 (psched_mtu() returning 0),
which spins sfq_dequeue() identically. sfq_change() already rejects a
negative quantum, so only the init path was exposed.
Conditions to recreate the bug: a device whose MTU (plus
hard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy
device with max_mtu == 0 accepting MTU 2147483634). Requires
CAP_NET_ADMIN in a user namespace.
net/sched: sfq: clamp quantum to avoid signed overflow soft lockup
sfq_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) (unsigned). A
device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU
2147483634) makes psched_mtu() return 0x80000000, so slot->allot = INT_MIN
and INT_MIN + INT_MIN toggles between INT_MIN and 0 forever, spinning
sfq_dequeue() under the qdisc lock.
Clamp the quantum to [256, 1 << 20] so the refill loop terminates. The
lower bound also covers q->quantum == 0 (psched_mtu() returning 0),
which spins sfq_dequeue() identically. sfq_change() already rejects a
negative quantum, so only the init path was exposed.
Conditions to recreate the bug: a device whose MTU (plus
hard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy
device with max_mtu == 0 accepting MTU 2147483634). Requires
CAP_NET_ADMIN in a user namespace.
Affected & Patched Versions
- Linux Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 86799499585af06a9431c9e7782658667bd62650
- Linux Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 2017c355a5a1af77736cd1739fe922f69b5652dc
- Linux Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 6581a82bf08ba5d4e2a6d4e3080df43315b296c4
- Linux Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 9d782c662879c3adaaca30e05c36910ad11b9e54
- Linux Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < d72dbdfaeb5b9b8d884e0e036c3442754379ef74
- Linux Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < aeb8196ecb95146e3410f635628e6cd47352b3e5
- Linux Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < da16c31517cd2c06bb2c78c73e91ae192c01c426
- Linux Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 816e90057ab1879562a5b7cc688e35bb9027ae97
- Linux Linux >= 2.6.12
- Linux Linux 86799499585af06a9431c9e7782658667bd62650
- Linux Linux 2017c355a5a1af77736cd1739fe922f69b5652dc
- Linux Linux 6581a82bf08ba5d4e2a6d4e3080df43315b296c4
- Linux Linux 9d782c662879c3adaaca30e05c36910ad11b9e54
- Linux Linux d72dbdfaeb5b9b8d884e0e036c3442754379ef74
- Linux Linux aeb8196ecb95146e3410f635628e6cd47352b3e5
- Linux Linux da16c31517cd2c06bb2c78c73e91ae192c01c426
- Linux Linux 816e90057ab1879562a5b7cc688e35bb9027ae97
External References
- https://git.kernel.org/stable/c/86799499585af06a9431c9e7782658667bd62650
- https://git.kernel.org/stable/c/2017c355a5a1af77736cd1739fe922f69b5652dc
- https://git.kernel.org/stable/c/6581a82bf08ba5d4e2a6d4e3080df43315b296c4
- https://git.kernel.org/stable/c/9d782c662879c3adaaca30e05c36910ad11b9e54
- https://git.kernel.org/stable/c/d72dbdfaeb5b9b8d884e0e036c3442754379ef74
- https://git.kernel.org/stable/c/aeb8196ecb95146e3410f635628e6cd47352b3e5
- https://git.kernel.org/stable/c/da16c31517cd2c06bb2c78c73e91ae192c01c426
- https://git.kernel.org/stable/c/816e90057ab1879562a5b7cc688e35bb9027ae97