net/sched: Fix mirred deadlock on device recursion
En bref
Sévérité
Non disponible
EPSS
EPSS 0.18 % · centile 7 (2026-10-27)
État
PUBLISHED
Publiée
Mise à jour
Attribuée par
Linux
Statut NVD
Modified
Description
In the Linux kernel, the following vulnerability has been resolved:
net/sched: Fix mirred deadlock on device recursion
When the mirred action is used on a classful egress qdisc and a packet is
mirrored or redirected to self we hit a qdisc lock deadlock.
See trace below.
[..... other info removed for brevity....]
[ 82.890906]
[ 82.890906] ============================================
[ 82.890906] WARNING: possible recursive locking detected
[ 82.890906] 6.8.0-05205-g77fadd89fe2d-dirty #213 Tainted: G W
[ 82.890906] --------------------------------------------
[ 82.890906] ping/418 is trying to acquire lock:
[ 82.890906] ffff888006994110 (&sch->q.lock){+.-.}-{3:3}, at:
__dev_queue_xmit+0x1778/0x3550
[ 82.890906]
[ 82.890906] but task is already holding lock:
[ 82.890906] ffff888006994110 (&sch->q.lock){+.-.}-{3:3}, at:
__dev_queue_xmit+0x1778/0x3550
[ 82.890906]
[ 82.890906] other info that might help us debug this:
[ 82.890906] Possible unsafe locking scenario:
[ 82.890906]
[ 82.890906] CPU0
[ 82.890906] ----
[ 82.890906] lock(&sch->q.lock);
[ 82.890906] lock(&sch->q.lock);
[ 82.890906]
[ 82.890906] *** DEADLOCK ***
[ 82.890906]
[..... other info removed for brevity....]
Example setup (eth0->eth0) to recreate
tc qdisc add dev eth0 root handle 1: htb default 30
tc filter add dev eth0 handle 1: protocol ip prio 2 matchall \
action mirred egress redirect dev eth0
Another example(eth0->eth1->eth0) to recreate
tc qdisc add dev eth0 root handle 1: htb default 30
tc filter add dev eth0 handle 1: protocol ip prio 2 matchall \
action mirred egress redirect dev eth1
tc qdisc add dev eth1 root handle 1: htb default 30
tc filter add dev eth1 handle 1: protocol ip prio 2 matchall \
action mirred egress redirect dev eth0
We fix this by adding an owner field (CPU id) to struct Qdisc set after
root qdisc is entered. When the softirq enters it a second time, if the
qdisc owner is the same CPU, the packet is dropped to break the loop.
