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-Url: https://git.stricted.de/?a=commitdiff_plain;h=c8b9a1fbd1fc6cdf1def415dc70e90d6a929a960;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git tracing/filter: Do not WARN on operand count going below zero 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@oracle.com Reported-by: Vince Weaver Reported-by: Sasha Levin Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index fe3e086d38e9..1c08866779f2 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -1342,7 +1342,9 @@ static int check_preds(struct filter_parse_state *ps) 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) {