CVE-2026-99141
Full vulnerability record from the local CVENow database.
Description
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.
View original CVE JSON
{
"id": "CVE-2026-99141",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-28T11:17:34.093",
"lastModified": "2026-10-28T11:17:34.093",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"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->current_trace_flags = t->flags ? : t->tracer->flags;\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->current_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 > /sys/kernel/tracing/current_tracer\n echo 1 > /sys/kernel/tracing/snapshot\n echo hwlat > /sys/kernel/tracing/current_tracer\n cat /sys/kernel/tracing/snapshot\n\nRather than teaching every user of tr->current_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."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"kernel/trace/trace.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "e29aa918a928408c3e64b0d1025e4eb9f6fc549e",
"lessThan": "b1547c6ba93b8863010aa324cd20c441f886f23e",
"versionType": "git",
"status": "affected"
},
{
"version": "e29aa918a928408c3e64b0d1025e4eb9f6fc549e",
"lessThan": "3cc117514d69067a94d6c7479730dce41e678f50",
"versionType": "git",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"kernel/trace/trace.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "6.19",
"status": "affected"
},
{
"version": "0",
"lessThan": "6.19",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2.13",
"lessThanOrEqual": "7.2.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.3",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/3cc117514d69067a94d6c7479730dce41e678f50",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/b1547c6ba93b8863010aa324cd20c441f886f23e",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}