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>

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index d96ba22dabfaaf38b9510c604050e07648119aa3..99e7e314e451ca1adee476781225faf5657be9f9 100644 (file)
--- 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;