Patch "tracing/filter: Do not WARN on operand count going below zero" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

tracing/filter: Do not WARN on operand count going below zero

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tracing-filter-do-not-warn-on-operand-count-going-below-zero.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Steven Rostedt (Red Hat)" <[email protected]>
Date: Thu, 25 Jun 2015 18:02:29 -0400
Subject: tracing/filter: Do not WARN on operand count going below zero

From: "Steven Rostedt (Red Hat)" <[email protected]>

commit b4875bbe7e68f139bd3383828ae8e994a0df6d28 upstream.

When testing the fix for the trace filter, I could not come up with a scenario where the operand count goes below zero, so I added a WARN_ON_ONCE(cnt < 0) to the logic. But there is legitimate case that it can happen (although the filter would be wrong).

 # echo '>' > /sys/kernel/debug/events/ext4/ext4_truncate_exit/filter

That is, a single operation without any operands will hit the path where the WARN_ON_ONCE() can trigger. Although this is harmless, and the filter is reported as a error. But instead of spitting out a warning to the kernel dmesg, just fail nicely and report it via the proper channels.

---
 kernel/trace/trace_events_filter.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -1413,7 +1413,9 @@ static int check_preds(struct filter_par
 			continue;
 		}
 		n_normal_preds++;
-		WARN_ON_ONCE(cnt < 0);
+		/* all ops should have operands */
+		if (cnt < 0)
+			break;
 	}
 
 	if (cnt != 1 || !n_normal_preds || n_logical_preds >= n_normal_preds) {

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/tracing-have-branch-tracer-use-recursive-field-of-task-struct.patch queue-3.14/tracing-filter-do-not-allow-infix-to-exceed-end-of-string.patch queue-3.14/tracing-filter-do-not-warn-on-operand-count-going-below-zero.patch