CVE-2026-74267

Status: UPDATED  |  Advisory ID: CVE-2026-74267

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

net/sched: sch_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen

Whenever codel drops packets during peek, it calls

qdisc_tree_reduce_backlog. An issue arises because it calls

qdisc_tree_reduce_backlog before it reincrements the qlen. If qlen drops

to zero, but peek returns an skb, the parent's qlen_notify callback will

be executed even though codel still has 1 packet on the queue and, thus,

will mistakenly deactivate the parent's class causing issues like a wild

memory access when qfq has codel as a child:

[ 36.339843][ T370] Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI

[ 36.340408][ T370] KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127]

[ 36.340737][ T370] CPU: 2 UID: 0 PID: 370 Comm: tc Not tainted 7.1.0-rc5-00287-g66e13b626592 #87 PREEMPT(full)

[ 36.341113][ T370] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011

[ 36.341357][ T370] RIP: 0010:qfq_deactivate_agg (include/linux/list.h:1029 (discriminator 2) include/linux/list.h:1043 (discriminator 2) net/sched/sch_qfq.c:1369 (discriminator 2) net/sched/sch_qfq.c:1395 (discriminator 2)) sch_qfq

[ 36.342221][ T370] RSP: 0018:ffff8881100ef370 EFLAGS: 00010216

[ 36.342422][ T370] RAX: 0000000000000000 RBX: ffff8881058a9568 RCX: dffffc0000000000

[ 36.342664][ T370] RDX: 1ffff11021064dc3 RSI: ffff888108326e00 RDI: dffffc0000000000

[ 36.342905][ T370] RBP: ffff8881058a8280 R08: dead000000000122 R09: 1bd5a00000000024

[ 36.343140][ T370] R10: fffffbfff2940329 R11: fffffbfff2940329 R12: 0000000000000000

[ 36.343383][ T370] R13: dead000000000100 R14: ffff8881058a9580 R15: ffff8881058a9578

[ 36.343631][ T370] FS: 00007fc04b0ca780(0000) GS:ffff888184fef000(0000) knlGS:0000000000000000

[ 36.343911][ T370] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

[ 36.344116][ T370] CR2: 0000557c02c02000 CR3: 000000010e0ba000 CR4: 0000000000750ef0

[ 36.344359][ T370] PKRU: 55555554

[ 36.344481][ T370] Call Trace:

...

[ 36.345054][ T370] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1487) sch_qfq

[ 36.345222][ T370] qdisc_reset (net/sched/sch_generic.c:1057)

[ 36.345503][ T370] __qdisc_destroy (net/sched/sch_generic.c:1096)

[ 36.345677][ T370] qdisc_graft (net/sched/sch_api.c:1062 net/sched/sch_api.c:1053 net/sched/sch_api.c:1159)

[ 36.346335][ T370] tc_get_qdisc (net/sched/sch_api.c:1528 net/sched/sch_api.c:1556)

Fix this by only calling qdisc_tree_reduce_backlog in peek after the

qlen is restored. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References