tracepoint: check if the probe has been registered (f66af459) · Commits · 戴 / test

Impact: fix kernel crash that can trigger during tracing If we try to remove a probe that has not been already registered, the tracepoint_entry_remove_probe() function will dereference a NULL pointer. Check the probe before removing it to avoid crashes. Signed-off-by:

Frederic Weisbecker <fweisbec@gmail.com> Acked-by:

Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Acked-by:

Steven Rostedt <srostedt@redhat.com> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/tracepoint.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -131,6 +131,9 @@ tracepoint_entry_remove_probe(struct tracepoint_entry entry, void probe)

		old = entry->funcs;

		if (!old)
		return NULL;

		debug_print_probes(entry);
		/* (N -> M), (N > 1, M >= 0) probes */
		for (nr_probes = 0; old[nr_probes]; nr_probes++) {
		@@ -388,6 +391,11 @@ int tracepoint_probe_unregister(const char name, void probe)
		if (entry->rcu_pending)
		rcu_barrier_sched();
		old = tracepoint_entry_remove_probe(entry, probe);
		if (!old) {
		printk(KERN_WARNING "Warning: Trying to unregister a probe"
		"that doesn't exist\n");
		goto end;
		}
		mutex_unlock(&tracepoints_mutex);
		tracepoint_update_probes(); /* may update entry */
		mutex_lock(&tracepoints_mutex);

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