{"id":"CVE-2026-99141","state":"PUBLISHED","title":"tracing: Fix crash in print_graph_function_event()","description":"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.","publishedAt":"2026-10-28T10:34:52.091Z","updatedAt":"2026-10-28T10:34:52.091Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e29aa918a928408c3e64b0d1025e4eb9f6fc549e","status":"affected","lessThan":"b1547c6ba93b8863010aa324cd20c441f886f23e","versionType":"git"},{"version":"e29aa918a928408c3e64b0d1025e4eb9f6fc549e","status":"affected","lessThan":"3cc117514d69067a94d6c7479730dce41e678f50","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.19","versionType":"semver"},{"version":"7.2.13","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace.c"]}],"references":["https://git.kernel.org/stable/c/b1547c6ba93b8863010aa324cd20c441f886f23e","https://git.kernel.org/stable/c/3cc117514d69067a94d6c7479730dce41e678f50"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/99xxx/CVE-2026-99141.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-99141","state":"PUBLISHED","datePublished":"2026-10-28T10:34:52.091Z","dateUpdated":"2026-10-28T10:34:52.091Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.395Z"},"containers":{"cna":{"title":"tracing: Fix crash in print_graph_function_event()","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":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e29aa918a928408c3e64b0d1025e4eb9f6fc549e","status":"affected","lessThan":"b1547c6ba93b8863010aa324cd20c441f886f23e","versionType":"git"},{"version":"e29aa918a928408c3e64b0d1025e4eb9f6fc549e","status":"affected","lessThan":"3cc117514d69067a94d6c7479730dce41e678f50","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.19","versionType":"semver"},{"version":"7.2.13","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/b1547c6ba93b8863010aa324cd20c441f886f23e"},{"url":"https://git.kernel.org/stable/c/3cc117514d69067a94d6c7479730dce41e678f50"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-28T10:34:52.091Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"7.2.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}