[tip:tracing/ftrace] tracing: fix oops in tracepoint_update_probe_range()

[Jaswinder Singh Rajput]

Commit-ID:  09933a108e6730a464a1ab676c9decc11aee0edc
Gitweb:     http://git.kernel.org/tip/09933a108e6730a464a1ab676c9decc11aee0edc
Author:     Jaswinder Singh Rajput <jaswinder@xxxxxxxxxx>
AuthorDate: Wed, 18 Mar 2009 22:18:56 +0530
Commit:     Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 18 Mar 2009 18:54:39 +0100

tracing: fix oops in tracepoint_update_probe_range()

Change this crash:

 BUG: unable to handle kernel NULL pointer dereference at (null)
 IP: [<ffffffff8107d4de>] tracepoint_update_probe_range+0x1f/0x9b
 PGD 13d5fb067 PUD 13d688067 PMD 0
 Oops: 0000 [#1] SMP

To a more debuggable WARN_ONCE().

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
LKML-Reference: <1237394936.3132.1.camel@xxxxxxxxxxxxxxxxxxxxx>
[ moved the check outside the lock and added a WARN_ON(). ]
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 kernel/tracepoint.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 7960274..adf2873 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -272,12 +272,17 @@ static void disable_tracepoint(struct tracepoint *elem)
  *
  * Updates the probe callback corresponding to a range of tracepoints.
  */
-void tracepoint_update_probe_range(struct tracepoint *begin,
-	struct tracepoint *end)
+void
+tracepoint_update_probe_range(struct tracepoint *begin, struct tracepoint *end)
 {
 	struct tracepoint *iter;
 	struct tracepoint_entry *mark_entry;
 
+	if (!begin) {
+		WARN_ON_ONCE(1);
+		return;
+	}
+
 	mutex_lock(&tracepoints_mutex);
 	for (iter = begin; iter < end; iter++) {
 		mark_entry = get_tracepoint(iter->name);
--
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