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Subject[PATCH][RESEND] tracepoint: Check if the probe has been registered
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>
---
kernel/tracepoint.c | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index f2b7c28..af8c856 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -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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