Description
In the Linux kernel, the following vulnerability has been resolved: net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs When shrinking the number of real tx queues, netif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush qdiscs for queues which will no longer be used. qdisc_reset_all_tx_gt() currently serializes qdisc_reset() with qdisc_lock(). However, for lockless qdiscs, the dequeue path is serialized by qdisc_run_begin/end() using qdisc->seqlock instead, so qdisc_reset() can run concurrently with __qdisc_run() and free skbs while they are still being dequeued, leading to UAF. This can easily be reproduced on e.g. virtio-net by imposing heavy traffic while frequently changing the number of queue pairs: iperf3 -ub0 -c $peer -t 0 & while :; do ethtool -L eth0 combined 1 ethtool -L eth0 combined 2 done With KASAN enabled, this leads to reports like: BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760 ... Call Trace: <TASK> ... __qdisc_run+0x133f/0x1760 __dev_queue_xmit+0x248f/0x3550 ip_finish_output2+0xa42/0x2110 ip_output+0x1a7/0x410 ip_send_skb+0x2e6/0x480 udp_send_skb+0xb0a/0x1590 udp_sendmsg+0x13c9/0x1fc0 ... </TASK> Allocated by task 1270 on cpu 5 at 44.558414s: ... alloc_skb_with_frags+0x84/0x7c0 sock_alloc_send_pskb+0x69a/0x830 __ip_append_data+0x1b86/0x48c0 ip_make_skb+0x1e8/0x2b0 udp_sendmsg+0x13a6/0x1fc0 ... Freed by task 1306 on cpu 3 at 44.558445s: ... kmem_cache_free+0x117/0x5e0 pfifo_fast_reset+0x14d/0x580 qdisc_reset+0x9e/0x5f0 netif_set_real_num_tx_queues+0x303/0x840 virtnet_set_channels+0x1bf/0x260 [virtio_net] ethnl_set_channels+0x684/0xae0 ethnl_default_set_doit+0x31a/0x890 ... Serialize qdisc_reset_all_tx_gt() against the lockless dequeue path by taking qdisc->seqlock for TCQ_F_NOLOCK qdiscs, matching the serialization model already used by dev_reset_queue(). Additionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state reflects an empty queue, avoiding needless re-scheduling.
Product status
6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 (git) before 5bb27ad54d12de67e457d7d251198e361bef835e
6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 (git) before 7594467c49bfc2f4644dee0415ac2290db11fa0d
6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 (git) before dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750
6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 (git) before 5bc4e69306ed7ae02232eb4c0b23ed621a26d504
6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 (git) before 8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb
6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 (git) before c69df4e0524f8de8e176ba389acd83e85f5f49d0
6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 (git) before 7f083faf59d14c04e01ec05a7507f036c965acf8
4.16
Any version before 4.16
5.15.203 (semver)
6.1.167 (semver)
6.6.130 (semver)
6.12.77 (semver)
6.18.17 (semver)
6.19.7 (semver)
7.0 (original_commit_for_fix)
References
git.kernel.org/...c/5bb27ad54d12de67e457d7d251198e361bef835e
git.kernel.org/...c/7594467c49bfc2f4644dee0415ac2290db11fa0d
git.kernel.org/...c/dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750
git.kernel.org/...c/5bc4e69306ed7ae02232eb4c0b23ed621a26d504
git.kernel.org/...c/8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb
git.kernel.org/...c/c69df4e0524f8de8e176ba389acd83e85f5f49d0
git.kernel.org/...c/7f083faf59d14c04e01ec05a7507f036c965acf8