tracepoints: Prevent null probe from being added

Somehow tracepoint_entry_add_probe() function allows a null probe function.
And, this may lead to unexpected results since the number of probe
functions in an entry can be counted by checking whether a probe is null
or not in the for-loop.
This patch prevents a null probe from being added.
In tracepoint_entry_remove_probe() function, checking probe parameter
within the for-loop is moved out for code efficiency, leaving the null probe
feature which removes all probe functions in the entry.

Link: http://lkml.kernel.org/r/1365991995-19445-1-git-send-email-kpark3469@gmail.com

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Sahara <keun-o.park@windriver.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 13 insertions, 8 deletions

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index d96ba22dabfa..99e7e314e451 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -112,7 +112,8 @@ tracepoint_entry_add_probe(struct tracepoint_entry *entry,
         int nr_probes = 0;
         struct tracepoint_func *old, *new;
 
-        WARN_ON(!probe);
+        if (WARN_ON(!probe))
+                return ERR_PTR(-EINVAL);
 
         debug_print_probes(entry);
         old = entry->funcs;
@@ -152,13 +153,18 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
 
         debug_print_probes(entry);
         /* (N -> M), (N > 1, M >= 0) probes */
-        for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
-                if (!probe ||
-                    (old[nr_probes].func == probe &&
-                     old[nr_probes].data == data))
-                        nr_del++;
+        if (probe) {
+                for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+                        if (old[nr_probes].func == probe &&
+                             old[nr_probes].data == data)
+                                nr_del++;
+                }
         }
 
+        /*
+         * If probe is NULL, then nr_probes = nr_del = 0, and then the
+         * entire entry will be removed.
+         */
         if (nr_probes - nr_del == 0) {
                 /* N -> 0, (N > 1) */
                 entry->funcs = NULL;
@@ -173,8 +179,7 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
                 if (new == NULL)
                         return ERR_PTR(-ENOMEM);
                 for (i = 0; old[i].func; i++)
-                        if (probe &&
-                            (old[i].func != probe || old[i].data != data))
+                        if (old[i].func != probe || old[i].data != data)
                                 new[j++] = old[i];
                 new[nr_probes - nr_del].func = NULL;
                 entry->refcount = nr_probes - nr_del;