net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs
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: ... __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 ... 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
CVE-2026-23340
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-23340
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7",
"lessThan": "5bb27ad54d12de67e457d7d251198e361bef835e",
"versionType": "git"
},
{
"status": "affected",
"version": "6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7",
"lessThan": "7594467c49bfc2f4644dee0415ac2290db11fa0d",
"versionType": "git"
},
{
"status": "affected",
"version": "6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7",
"lessThan": "dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750",
"versionType": "git"
},
{
"status": "affected",
"version": "6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7",
"lessThan": "5bc4e69306ed7ae02232eb4c0b23ed621a26d504",
"versionType": "git"
},
{
"status": "affected",
"version": "6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7",
"lessThan": "8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb",
"versionType": "git"
},
{
"status": "affected",
"version": "6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7",
"lessThan": "c69df4e0524f8de8e176ba389acd83e85f5f49d0",
"versionType": "git"
},
{
"status": "affected",
"version": "6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7",
"lessThan": "7f083faf59d14c04e01ec05a7507f036c965acf8",
"versionType": "git"
}
],
"programFiles": [
"include/net/sch_generic.h"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.16"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.16",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.15.203",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.167",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.130",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.77",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.17",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "6.19.7",
"versionType": "semver",
"lessThanOrEqual": "6.19.*"
},
{
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"include/net/sch_generic.h"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-23340
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #39840 · Revision 1
- Added to Heist Feed
- Publisher date