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tracepoint: check if the probe has been registered

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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>
This commit is contained in:
Frederic Weisbecker 2008-10-22 19:14:55 +02:00 committed by Ingo Molnar
parent 5209f08dc8
commit f66af459a9
1 changed files with 8 additions and 0 deletions
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8
kernel/tracepoint.c
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@ -131,6 +131,9 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe)
old = entry->funcs; old = entry->funcs;
if (!old)
return NULL;
debug_print_probes(entry); debug_print_probes(entry);
/* (N -> M), (N > 1, M >= 0) probes */ /* (N -> M), (N > 1, M >= 0) probes */
for (nr_probes = 0; old[nr_probes]; nr_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) if (entry->rcu_pending)
rcu_barrier_sched(); rcu_barrier_sched();
old = tracepoint_entry_remove_probe(entry, probe); 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); mutex_unlock(&tracepoints_mutex);
tracepoint_update_probes(); /* may update entry */ tracepoint_update_probes(); /* may update entry */
mutex_lock(&tracepoints_mutex); mutex_lock(&tracepoints_mutex);