CVE-2026-99141 (GCVE-0-2026-99141)

Vulnerability from cvelistv5 – Published: 2026-10-28 10:34 – Updated: 2026-10-28 10:34
VLAI
Title
tracing: Fix crash in print_graph_function_event()
Summary
In the Linux kernel, the following vulnerability has been resolved: tracing: Fix crash in print_graph_function_event() tracing_set_tracer() assigns the flags of the newly selected tracer with: tr->current_trace_flags = t->flags ? : t->tracer->flags; If the new tracer defines neither static flags nor default flags, like hwlat, irqsoff or wakeup, add_tracer() has no per instance flags copy for it, and both operands are NULL, so tr->current_trace_flags ends up being NULL as well. The ring buffer is not cleared when switching tracers: it is reset inside tracer_init(), after current_trace_flags was already assigned. If the buffer still holds function_graph entries of the previous tracer, printing one of them dereferences the NULL pointer. This was hit by cat trace during an ftrace stress test: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode RIP: 0010:print_graph_function_event+0xe/0x20 Call Trace: s_show+0x4d/0x110 seq_read_iter+0x2d4/0x490 seq_read+0x130/0x170 vfs_read+0xb5/0x370 ksys_read+0x6d/0xe0 do_syscall_64+0xbc/0x450 The snapshot buffer is not reset at all, so this can be reproduced without a race: echo function_graph > /sys/kernel/tracing/current_tracer echo 1 > /sys/kernel/tracing/snapshot echo hwlat > /sys/kernel/tracing/current_tracer cat /sys/kernel/tracing/snapshot Rather than teaching every user of tr->current_trace_flags about this corner case, make sure it is never NULL: when the newly selected tracer has no flags at all, tracing_set_tracer() falls back to a static empty no_tracer_flags. run_tracer_selftest() can hit the same case, so the same fallback is added there too. The existing users already handle opts == NULL, so these tracers keep behaving as before.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7033 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e29aa918a928408c3e64b0d1025e4eb9f6fc549e , < b1547c6ba93b8863010aa324cd20c441f886f23e (git)
Affected: e29aa918a928408c3e64b0d1025e4eb9f6fc549e , < 3cc117514d69067a94d6c7479730dce41e678f50 (git)
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Linux Linux Affected: 6.19
Unaffected: 0 , < 6.19 (semver)
Unaffected: 7.2.13 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix crash in print_graph_function_event()\n\ntracing_set_tracer() assigns the flags of the newly selected tracer\nwith:\n\n\ttr-\u003ecurrent_trace_flags = t-\u003eflags ? : t-\u003etracer-\u003eflags;\n\nIf the new tracer defines neither static flags nor default flags, like\nhwlat, irqsoff or wakeup, add_tracer() has no per instance flags copy\nfor it, and both operands are NULL, so tr-\u003ecurrent_trace_flags ends up\nbeing NULL as well.\n\nThe ring buffer is not cleared when switching tracers: it is reset\ninside tracer_init(), after current_trace_flags was already assigned.\nIf the buffer still holds function_graph entries of the previous\ntracer, printing one of them dereferences the NULL pointer. This was\nhit by cat trace during an ftrace stress test:\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000000\n  #PF: supervisor read access in kernel mode\n  RIP: 0010:print_graph_function_event+0xe/0x20\n  Call Trace:\n   s_show+0x4d/0x110\n   seq_read_iter+0x2d4/0x490\n   seq_read+0x130/0x170\n   vfs_read+0xb5/0x370\n   ksys_read+0x6d/0xe0\n   do_syscall_64+0xbc/0x450\n\nThe snapshot buffer is not reset at all, so this can be reproduced\nwithout a race:\n\n  echo function_graph \u003e /sys/kernel/tracing/current_tracer\n  echo 1 \u003e /sys/kernel/tracing/snapshot\n  echo hwlat \u003e /sys/kernel/tracing/current_tracer\n  cat /sys/kernel/tracing/snapshot\n\nRather than teaching every user of tr-\u003ecurrent_trace_flags about this\ncorner case, make sure it is never NULL: when the newly selected\ntracer has no flags at all, tracing_set_tracer() falls back to a\nstatic empty no_tracer_flags. run_tracer_selftest() can hit the same\ncase, so the same fallback is added there too. The existing users\nalready handle opts == NULL, so these tracers keep behaving as before."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-10-28T10:34:52.091Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "title": "tracing: Fix crash in print_graph_function_event()",
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    "datePublished": "2026-10-28T10:34:52.091Z",
    "dateReserved": "2026-09-25T10:25:14.395Z",
    "dateUpdated": "2026-10-28T10:34:52.091Z",
    "state": "PUBLISHED"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix crash in print_graph_function_event()\n\ntracing_set_tracer() assigns the flags of the newly selected tracer\nwith:\n\n\ttr-\u003ecurrent_trace_flags = t-\u003eflags ? : t-\u003etracer-\u003eflags;\n\nIf the new tracer defines neither static flags nor default flags, like\nhwlat, irqsoff or wakeup, add_tracer() has no per instance flags copy\nfor it, and both operands are NULL, so tr-\u003ecurrent_trace_flags ends up\nbeing NULL as well.\n\nThe ring buffer is not cleared when switching tracers: it is reset\ninside tracer_init(), after current_trace_flags was already assigned.\nIf the buffer still holds function_graph entries of the previous\ntracer, printing one of them dereferences the NULL pointer. This was\nhit by cat trace during an ftrace stress test:\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000000\n  #PF: supervisor read access in kernel mode\n  RIP: 0010:print_graph_function_event+0xe/0x20\n  Call Trace:\n   s_show+0x4d/0x110\n   seq_read_iter+0x2d4/0x490\n   seq_read+0x130/0x170\n   vfs_read+0xb5/0x370\n   ksys_read+0x6d/0xe0\n   do_syscall_64+0xbc/0x450\n\nThe snapshot buffer is not reset at all, so this can be reproduced\nwithout a race:\n\n  echo function_graph \u003e /sys/kernel/tracing/current_tracer\n  echo 1 \u003e /sys/kernel/tracing/snapshot\n  echo hwlat \u003e /sys/kernel/tracing/current_tracer\n  cat /sys/kernel/tracing/snapshot\n\nRather than teaching every user of tr-\u003ecurrent_trace_flags about this\ncorner case, make sure it is never NULL: when the newly selected\ntracer has no flags at all, tracing_set_tracer() falls back to a\nstatic empty no_tracer_flags. run_tracer_selftest() can hit the same\ncase, so the same fallback is added there too. The existing users\nalready handle opts == NULL, so these tracers keep behaving as before."
          }
        ],
        "id": "CVE-2026-99141",
        "lastModified": "2026-10-28T11:17:34.093",
        "metrics": {},
        "published": "2026-10-28T11:17:34.093",
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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}



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