systrap: fix TOCTOU on ThreadID in NotifyInterrupt#12935
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copybara-service[bot] merged 2 commits intomasterfrom Apr 13, 2026
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systrap: fix TOCTOU on ThreadID in NotifyInterrupt#12935copybara-service[bot] merged 2 commits intomasterfrom
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NotifyInterrupt reads ThreadID from guest-writable shared memory twice: once to check for invalidThreadID and again after acquiring the lock for the map lookup. A malicious guest can modify ThreadID between these two reads. If the guest sets ThreadID to a recently-exited thread between the reads, the TGKILL returns ESRCH which marks the subprocess as dead and kills the syscall thread. If the guest engineers a non-ESRCH error, the sentry panics. Read ThreadID exactly once into a local variable and use it for both the early-return check and the map lookup. This eliminates the TOCTOU window.
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systrap: fix TOCTOU on ThreadID in NotifyInterrupt
NotifyInterrupt reads ThreadID from guest-writable shared memory twice: once to check for invalidThreadID (line 129) and again after acquiring the lock for the map lookup (line 136). A malicious guest can modify ThreadID between these two reads.
If the guest sets ThreadID to a recently-exited thread, TGKILL returns ESRCH which marks the subprocess as dead and kills the syscall thread. If the guest engineers a non-ESRCH error, the sentry panics (line 157).
Fix: read ThreadID exactly once into a local variable and use it for both the early-return check and the map lookup.
FUTURE_COPYBARA_INTEGRATE_REVIEW=#12927 from ibondarenko1:fix-systrap-threadid-toctou 2a22300