tracing: Fix NULL pointer dereference in module event cache removal

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74633
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-22 16:16:36 UTC
Updated2026-08-22 16:16:36 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: tracing: Fix NULL pointer dereference in module event cache removal A module-only event filter such as ":mod:foo" is cached with a NULL event_mod->match when foo has not been loaded. If a later write tries to remove a specific match from the same module, remove_cache_mod() passes the NULL cached match to strcmp(), causing a NULL pointer dereference. The issue can be reproduced from userspace: echo ':mod:trace_events_kunit_missing' > /sys/kernel/tracing/set_event echo '!foo_bar:mod:trace_events_kunit_missing' >> /sys/kernel/tracing/set_event The second write must be a concatenation (">>") to not include O_TRUNC as that would cause ftrace_clear_events() to clear the cached modules lines. The crash was reproduced on x86_64 QEMU while KUnit workers contended on the event tracing path: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode RIP: 0010:strcmp+0x10/0x30 Call Trace: __ftrace_set_clr_event_nolock+0x373/0x4a0 ftrace_set_clr_event+0xf0/0x180 ftrace_event_write+0xdf/0x110 vfs_write+0xf6/0x440 ksys_write+0x68/0xe0 do_syscall_64+0xf9/0x540 entry_SYSCALL_64_after_hwframe+0x77/0x7f Check event_mod->match before comparing it, consistent with the existing NULL checks for the cached system and event fields. The mismatched removal continues to return -EINVAL; a broad cached module filter is removed with "!:mod:<module>".

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected b355247df104ef6644288884afd2c08b7bf49897 152a00440dc6ef62c6e4cf9bd881a7e6bb81fda9 git Not specified
CNA Linux Linux affected b355247df104ef6644288884afd2c08b7bf49897 ad4e9dd5fec7a322a471ff36fb9c76214e3c6992 git Not specified
CNA Linux Linux affected b355247df104ef6644288884afd2c08b7bf49897 b69859204d4db3acd86c1c2dadcef0d77b451933 git Not specified
CNA Linux Linux affected 6.14 Not specified
CNA Linux Linux unaffected 6.14 semver Not specified
CNA Linux Linux unaffected 6.18.45 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.9 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/b69859204d4db3acd86c1c2dadcef0d77b451933 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/152a00440dc6ef62c6e4cf9bd881a7e6bb81fda9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ad4e9dd5fec7a322a471ff36fb9c76214e3c6992 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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