CVE-2026-43385 (GCVE-0-2026-43385)

Vulnerability from cvelistv5 – Published: 2026-05-08 14:21 – Updated: 2026-05-08 14:21
VLAI?
Title
net: Fix rcu_tasks stall in threaded busypoll
Summary
In the Linux kernel, the following vulnerability has been resolved: net: Fix rcu_tasks stall in threaded busypoll I was debugging a NIC driver when I noticed that when I enable threaded busypoll, bpftrace hangs when starting up. dmesg showed: rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 10658 jiffies old. rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 40793 jiffies old. rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 131273 jiffies old. rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 402058 jiffies old. INFO: rcu_tasks detected stalls on tasks: 00000000769f52cd: .N nvcsw: 2/2 holdout: 1 idle_cpu: -1/64 task:napi/eth2-8265 state:R running task stack:0 pid:48300 tgid:48300 ppid:2 task_flags:0x208040 flags:0x00004000 Call Trace: <TASK> ? napi_threaded_poll_loop+0x27c/0x2c0 ? __pfx_napi_threaded_poll+0x10/0x10 ? napi_threaded_poll+0x26/0x80 ? kthread+0xfa/0x240 ? __pfx_kthread+0x10/0x10 ? ret_from_fork+0x31/0x50 ? __pfx_kthread+0x10/0x10 ? ret_from_fork_asm+0x1a/0x30 </TASK> The cause is that in threaded busypoll, the main loop is in napi_threaded_poll rather than napi_threaded_poll_loop, where the latter rarely iterates more than once within its loop. For rcu_softirq_qs_periodic inside napi_threaded_poll_loop to report its qs state, the last_qs must be 100ms behind, and this can't happen because napi_threaded_poll_loop rarely iterates in threaded busypoll, and each time napi_threaded_poll_loop is called last_qs is reset to latest jiffies. This patch changes so that in threaded busypoll, last_qs is saved in the outer napi_threaded_poll, and whether busy_poll_last_qs is NULL indicates whether napi_threaded_poll_loop is called for busypoll. This way last_qs would not reset to latest jiffies on each invocation of napi_threaded_poll_loop.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: c18d4b190a46651726c9a952667c74d2deb33c28 , < 52459201d0df3fdbb1d281738b7b772e2cacb49c (git)
Affected: c18d4b190a46651726c9a952667c74d2deb33c28 , < 1a86a1f7d88996085934139fa4c063b6299a2dd3 (git)
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    Linux Linux Affected: 6.19
Unaffected: 0 , < 6.19 (semver)
Unaffected: 6.19.9 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/dev.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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          "vendor": "Linux",
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              "version": "0",
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              "status": "unaffected",
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              "versionType": "semver"
            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
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      ],
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          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.9",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "7.0",
                  "versionStartIncluding": "6.19",
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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: Fix rcu_tasks stall in threaded busypoll\n\nI was debugging a NIC driver when I noticed that when I enable\nthreaded busypoll, bpftrace hangs when starting up. dmesg showed:\n\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 10658 jiffies old.\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 40793 jiffies old.\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 131273 jiffies old.\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 402058 jiffies old.\n  INFO: rcu_tasks detected stalls on tasks:\n  00000000769f52cd: .N nvcsw: 2/2 holdout: 1 idle_cpu: -1/64\n  task:napi/eth2-8265  state:R  running task     stack:0     pid:48300 tgid:48300 ppid:2      task_flags:0x208040 flags:0x00004000\n  Call Trace:\n   \u003cTASK\u003e\n   ? napi_threaded_poll_loop+0x27c/0x2c0\n   ? __pfx_napi_threaded_poll+0x10/0x10\n   ? napi_threaded_poll+0x26/0x80\n   ? kthread+0xfa/0x240\n   ? __pfx_kthread+0x10/0x10\n   ? ret_from_fork+0x31/0x50\n   ? __pfx_kthread+0x10/0x10\n   ? ret_from_fork_asm+0x1a/0x30\n   \u003c/TASK\u003e\n\nThe cause is that in threaded busypoll, the main loop is in\nnapi_threaded_poll rather than napi_threaded_poll_loop, where the\nlatter rarely iterates more than once within its loop. For\nrcu_softirq_qs_periodic inside napi_threaded_poll_loop to report its\nqs state, the last_qs must be 100ms behind, and this can\u0027t happen\nbecause napi_threaded_poll_loop rarely iterates in threaded busypoll,\nand each time napi_threaded_poll_loop is called last_qs is reset to\nlatest jiffies.\n\nThis patch changes so that in threaded busypoll, last_qs is saved\nin the outer napi_threaded_poll, and whether busy_poll_last_qs\nis NULL indicates whether napi_threaded_poll_loop is called for\nbusypoll. This way last_qs would not reset to latest jiffies on\neach invocation of napi_threaded_poll_loop."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-08T14:21:32.007Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/52459201d0df3fdbb1d281738b7b772e2cacb49c"
        },
        {
          "url": "https://git.kernel.org/stable/c/1a86a1f7d88996085934139fa4c063b6299a2dd3"
        }
      ],
      "title": "net: Fix rcu_tasks stall in threaded busypoll",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43385",
    "datePublished": "2026-05-08T14:21:32.007Z",
    "dateReserved": "2026-05-01T14:12:56.006Z",
    "dateUpdated": "2026-05-08T14:21:32.007Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-43385\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-08T15:16:49.830\",\"lastModified\":\"2026-05-08T15:16:49.830\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: Fix rcu_tasks stall in threaded busypoll\\n\\nI was debugging a NIC driver when I noticed that when I enable\\nthreaded busypoll, bpftrace hangs when starting up. dmesg showed:\\n\\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 10658 jiffies old.\\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 40793 jiffies old.\\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 131273 jiffies old.\\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 402058 jiffies old.\\n  INFO: rcu_tasks detected stalls on tasks:\\n  00000000769f52cd: .N nvcsw: 2/2 holdout: 1 idle_cpu: -1/64\\n  task:napi/eth2-8265  state:R  running task     stack:0     pid:48300 tgid:48300 ppid:2      task_flags:0x208040 flags:0x00004000\\n  Call Trace:\\n   \u003cTASK\u003e\\n   ? napi_threaded_poll_loop+0x27c/0x2c0\\n   ? __pfx_napi_threaded_poll+0x10/0x10\\n   ? napi_threaded_poll+0x26/0x80\\n   ? kthread+0xfa/0x240\\n   ? __pfx_kthread+0x10/0x10\\n   ? ret_from_fork+0x31/0x50\\n   ? __pfx_kthread+0x10/0x10\\n   ? ret_from_fork_asm+0x1a/0x30\\n   \u003c/TASK\u003e\\n\\nThe cause is that in threaded busypoll, the main loop is in\\nnapi_threaded_poll rather than napi_threaded_poll_loop, where the\\nlatter rarely iterates more than once within its loop. For\\nrcu_softirq_qs_periodic inside napi_threaded_poll_loop to report its\\nqs state, the last_qs must be 100ms behind, and this can\u0027t happen\\nbecause napi_threaded_poll_loop rarely iterates in threaded busypoll,\\nand each time napi_threaded_poll_loop is called last_qs is reset to\\nlatest jiffies.\\n\\nThis patch changes so that in threaded busypoll, last_qs is saved\\nin the outer napi_threaded_poll, and whether busy_poll_last_qs\\nis NULL indicates whether napi_threaded_poll_loop is called for\\nbusypoll. This way last_qs would not reset to latest jiffies on\\neach invocation of napi_threaded_poll_loop.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1a86a1f7d88996085934139fa4c063b6299a2dd3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/52459201d0df3fdbb1d281738b7b772e2cacb49c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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