[PATCH 3.4 46/65] tracing/filter: Do not WARN on operand count going below zero
From: lizf
Date: Mon Oct 19 2015 - 20:57:23 EST
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
3.4.110-rc1 review patch. If anyone has any objections, please let me know.
------------------
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.
Link: http://lkml.kernel.org/r/558C6082.90608@xxxxxxxxxx
Reported-by: Vince Weaver <vincent.weaver@xxxxxxxxx>
Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
---
kernel/trace/trace_events_filter.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 3b04aec..ae6c572 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1372,7 +1372,9 @@ static int check_preds(struct filter_parse_state *ps)
}
cnt--;
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) {
--
1.9.1
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