{"id":"CVE-2026-99141","title":"tracing: Fix crash in print_graph_function_event()","summary":"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…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= e29aa918a928408c3e64b0d1025e4eb9f6fc549e < b1547c6ba93b8863010aa324cd20c441f886f23e","Linux >= e29aa918a928408c3e64b0d1025e4eb9f6fc549e < 3cc117514d69067a94d6c7479730dce41e678f50","Linux 6.19"],"published":"2026-10-28","updated":"2026-10-28","sourceUpdated":"2026-10-28T10:34:52.091Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99141","references":[{"url":"https://git.kernel.org/stable/c/b1547c6ba93b8863010aa324cd20c441f886f23e"},{"url":"https://git.kernel.org/stable/c/3cc117514d69067a94d6c7479730dce41e678f50"}],"tags":["cve.org"],"ingestedAt":"2026-10-28T11:09:40.425Z","slug":"CVE-2026-99141","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= e29aa918a928408c3e64b0d1025e4eb9f6fc549e < b1547c6ba93b8863010aa324cd20c441f886f23e`\n- `Linux >= e29aa918a928408c3e64b0d1025e4eb9f6fc549e < 3cc117514d69067a94d6c7479730dce41e678f50`\n- `Linux 6.19`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}