From: Steven Rostedt (Red Hat) Date: Thu, 25 Jun 2015 22:02:29 +0000 (-0400) Subject: tracing/filter: Do not WARN on operand count going below zero X-Git-Tag: omap-for-v4.2/fixes-rc1^2~96^2~2 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=b4875bbe7e68f139bd3383828ae8e994a0df6d28 tracing/filter: Do not WARN on operand count going below zero 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@oracle.com Reported-by: Vince Weaver Reported-by: Sasha Levin Cc: stable@vger.kernel.org # 2.6.33+ Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 7f2e97ce71a7..2900d7723d97 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -1385,7 +1385,9 @@ static int check_preds(struct filter_parse_state *ps) if (elt->op != OP_NOT) 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) {