{"id":"CVE-2026-99141","aliases":[],"title":"tracing: Fix crash in print_graph_function_event()","titleSource":"Linux","descriptionSource":"Linux","products":[{"vendor":"Linux","name":"Linux","platforms":[],"versions":[{"version":"e29aa918a928408c3e64b0d1025e4eb9f6fc549e","status":"affected","lessThan":"b1547c6ba93b8863010aa324cd20c441f886f23e","versionType":"git"},{"version":"e29aa918a928408c3e64b0d1025e4eb9f6fc549e","status":"affected","lessThan":"3cc117514d69067a94d6c7479730dce41e678f50","versionType":"git"}],"defaultStatus":"unaffected","source":"Linux","url":"https://www.cve.org/CVERecord?id=CVE-2026-99141"},{"vendor":"Linux","name":"Linux","platforms":[],"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"}],"defaultStatus":"affected","source":"Linux","url":"https://www.cve.org/CVERecord?id=CVE-2026-99141"}],"remediation":[],"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.","severity":"unknown","score":null,"published":"2026-10-28T10:34:52.091Z","modified":"2026-10-28T10:34:52.091Z","withdrawn":false,"knownExploited":false,"affected":[],"references":["https://git.kernel.org/stable/c/b1547c6ba93b8863010aa324cd20c441f886f23e","https://git.kernel.org/stable/c/3cc117514d69067a94d6c7479730dce41e678f50"],"sources":[{"name":"CVE","id":"CVE-2026-99141","modified":"2026-10-28T10:34:52.091Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-99141"}],"assessments":[],"sourceAffected":[],"kev":{"status":"not-listed","checkedAt":"2026-10-28T15:40:31.878Z"},"coverage":[{"source":"NVD","status":"not-checked"},{"source":"GHSA","status":"not-checked"},{"source":"EUVD","status":"not-checked"},{"source":"EPSS","status":"not-checked"}],"evidence":[]}