{"cve":"CVE-2026-99141","nvd":{"published":"2026-10-28T11:17:34.093","modified":"2026-10-28T11:17:34.093","status":"Received","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.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/3cc117514d69067a94d6c7479730dce41e678f50","https://git.kernel.org/stable/c/b1547c6ba93b8863010aa324cd20c441f886f23e"],"products":[],"source":"nvd","synced_at":"2026-10-28T11:37:51.394563875+00:00"},"epss":null,"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}