CVE-2026-23340 (GCVE-0-2026-23340)

Vulnerability from cvelistv5 – Published: 2026-03-25 10:27 – Updated: 2026-03-25 10:27
VLAI?
Title
net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs
Summary
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 7594467c49bfc2f4644dee0415ac2290db11fa0d (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750 (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 5bc4e69306ed7ae02232eb4c0b23ed621a26d504 (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < c69df4e0524f8de8e176ba389acd83e85f5f49d0 (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 7f083faf59d14c04e01ec05a7507f036c965acf8 (git)
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    Linux Linux Affected: 4.16
Unaffected: 0 , < 4.16 (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.77 , ≤ 6.12.* (semver)
Unaffected: 6.18.17 , ≤ 6.18.* (semver)
Unaffected: 6.19.7 , ≤ 6.19.* (semver)
Unaffected: 7.0-rc3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/sch_generic.h"
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          "vendor": "Linux",
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              "version": "6.12.77",
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "6.19.7",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
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      ],
      "cpeApplicability": [
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          "nodes": [
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs\n\nWhen shrinking the number of real tx queues,\nnetif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush\nqdiscs for queues which will no longer be used.\n\nqdisc_reset_all_tx_gt() currently serializes qdisc_reset() with\nqdisc_lock(). However, for lockless qdiscs, the dequeue path is\nserialized by qdisc_run_begin/end() using qdisc-\u003eseqlock instead, so\nqdisc_reset() can run concurrently with __qdisc_run() and free skbs\nwhile they are still being dequeued, leading to UAF.\n\nThis can easily be reproduced on e.g. virtio-net by imposing heavy\ntraffic while frequently changing the number of queue pairs:\n\n  iperf3 -ub0 -c $peer -t 0 \u0026\n  while :; do\n    ethtool -L eth0 combined 1\n    ethtool -L eth0 combined 2\n  done\n\nWith KASAN enabled, this leads to reports like:\n\n  BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760\n  ...\n  Call Trace:\n   \u003cTASK\u003e\n   ...\n   __qdisc_run+0x133f/0x1760\n   __dev_queue_xmit+0x248f/0x3550\n   ip_finish_output2+0xa42/0x2110\n   ip_output+0x1a7/0x410\n   ip_send_skb+0x2e6/0x480\n   udp_send_skb+0xb0a/0x1590\n   udp_sendmsg+0x13c9/0x1fc0\n   ...\n   \u003c/TASK\u003e\n\n  Allocated by task 1270 on cpu 5 at 44.558414s:\n   ...\n   alloc_skb_with_frags+0x84/0x7c0\n   sock_alloc_send_pskb+0x69a/0x830\n   __ip_append_data+0x1b86/0x48c0\n   ip_make_skb+0x1e8/0x2b0\n   udp_sendmsg+0x13a6/0x1fc0\n   ...\n\n  Freed by task 1306 on cpu 3 at 44.558445s:\n   ...\n   kmem_cache_free+0x117/0x5e0\n   pfifo_fast_reset+0x14d/0x580\n   qdisc_reset+0x9e/0x5f0\n   netif_set_real_num_tx_queues+0x303/0x840\n   virtnet_set_channels+0x1bf/0x260 [virtio_net]\n   ethnl_set_channels+0x684/0xae0\n   ethnl_default_set_doit+0x31a/0x890\n   ...\n\nSerialize qdisc_reset_all_tx_gt() against the lockless dequeue path by\ntaking qdisc-\u003eseqlock for TCQ_F_NOLOCK qdiscs, matching the\nserialization model already used by dev_reset_queue().\n\nAdditionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state\nreflects an empty queue, avoiding needless re-scheduling."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-03-25T10:27:28.728Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7594467c49bfc2f4644dee0415ac2290db11fa0d"
        },
        {
          "url": "https://git.kernel.org/stable/c/dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750"
        },
        {
          "url": "https://git.kernel.org/stable/c/5bc4e69306ed7ae02232eb4c0b23ed621a26d504"
        },
        {
          "url": "https://git.kernel.org/stable/c/8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb"
        },
        {
          "url": "https://git.kernel.org/stable/c/c69df4e0524f8de8e176ba389acd83e85f5f49d0"
        },
        {
          "url": "https://git.kernel.org/stable/c/7f083faf59d14c04e01ec05a7507f036c965acf8"
        }
      ],
      "title": "net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-23340",
    "datePublished": "2026-03-25T10:27:28.728Z",
    "dateReserved": "2026-01-13T15:37:45.998Z",
    "dateUpdated": "2026-03-25T10:27:28.728Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23340\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-03-25T11:16:31.837\",\"lastModified\":\"2026-03-25T15:41:33.977\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs\\n\\nWhen shrinking the number of real tx queues,\\nnetif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush\\nqdiscs for queues which will no longer be used.\\n\\nqdisc_reset_all_tx_gt() currently serializes qdisc_reset() with\\nqdisc_lock(). However, for lockless qdiscs, the dequeue path is\\nserialized by qdisc_run_begin/end() using qdisc-\u003eseqlock instead, so\\nqdisc_reset() can run concurrently with __qdisc_run() and free skbs\\nwhile they are still being dequeued, leading to UAF.\\n\\nThis can easily be reproduced on e.g. virtio-net by imposing heavy\\ntraffic while frequently changing the number of queue pairs:\\n\\n  iperf3 -ub0 -c $peer -t 0 \u0026\\n  while :; do\\n    ethtool -L eth0 combined 1\\n    ethtool -L eth0 combined 2\\n  done\\n\\nWith KASAN enabled, this leads to reports like:\\n\\n  BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760\\n  ...\\n  Call Trace:\\n   \u003cTASK\u003e\\n   ...\\n   __qdisc_run+0x133f/0x1760\\n   __dev_queue_xmit+0x248f/0x3550\\n   ip_finish_output2+0xa42/0x2110\\n   ip_output+0x1a7/0x410\\n   ip_send_skb+0x2e6/0x480\\n   udp_send_skb+0xb0a/0x1590\\n   udp_sendmsg+0x13c9/0x1fc0\\n   ...\\n   \u003c/TASK\u003e\\n\\n  Allocated by task 1270 on cpu 5 at 44.558414s:\\n   ...\\n   alloc_skb_with_frags+0x84/0x7c0\\n   sock_alloc_send_pskb+0x69a/0x830\\n   __ip_append_data+0x1b86/0x48c0\\n   ip_make_skb+0x1e8/0x2b0\\n   udp_sendmsg+0x13a6/0x1fc0\\n   ...\\n\\n  Freed by task 1306 on cpu 3 at 44.558445s:\\n   ...\\n   kmem_cache_free+0x117/0x5e0\\n   pfifo_fast_reset+0x14d/0x580\\n   qdisc_reset+0x9e/0x5f0\\n   netif_set_real_num_tx_queues+0x303/0x840\\n   virtnet_set_channels+0x1bf/0x260 [virtio_net]\\n   ethnl_set_channels+0x684/0xae0\\n   ethnl_default_set_doit+0x31a/0x890\\n   ...\\n\\nSerialize qdisc_reset_all_tx_gt() against the lockless dequeue path by\\ntaking qdisc-\u003eseqlock for TCQ_F_NOLOCK qdiscs, matching the\\nserialization model already used by dev_reset_queue().\\n\\nAdditionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state\\nreflects an empty queue, avoiding needless re-scheduling.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/5bc4e69306ed7ae02232eb4c0b23ed621a26d504\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7594467c49bfc2f4644dee0415ac2290db11fa0d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7f083faf59d14c04e01ec05a7507f036c965acf8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c69df4e0524f8de8e176ba389acd83e85f5f49d0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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