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perf machine: Fix NULL parent dereference in fork event processing

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machine__process_fork_event() calls machine__findnew_thread() for the
parent thread, which can return NULL on allocation failure.  The code
then dereferences parent via thread__pid(parent) without a NULL check
when validating whether the parent PID matches.  The later NULL check
at thread__fork() does not prevent this earlier dereference.

Add a NULL guard before accessing the parent thread.

Fixes: 5cb73340d9 ("perf tools: Make fork event processing more resilient")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Arnaldo Carvalho de Melo 2026-07-26 20:40:08 -03:00 committed by Namhyung Kim
parent 23010160bb
commit 73ac546bd6
1 changed files with 2 additions and 1 deletions
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3
tools/perf/util/machine.c
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@ -1923,7 +1923,8 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
* (fork) event that would have removed the thread was lost. Assume the
* latter case and continue on as best we can.
*/
if (thread__pid(parent) != (pid_t)event->fork.ppid) {
if (parent != NULL &&
thread__pid(parent) != (pid_t)event->fork.ppid) {
dump_printf("removing erroneous parent thread %d/%d\n",
thread__pid(parent), thread__tid(parent));
machine__remove_thread(machine, parent);