[tip: perf/core] perf/core: Fix reversed NULL check in perf_event_groups_less()

["tip-bot2 for Dan Carpenter" <tip-bot2@linutronix.de>]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     a6763625ae6f8aa5ee82fcd8fa4e5e38db20dbc6
Gitweb:        https://git.kernel.org/tip/a6763625ae6f8aa5ee82fcd8fa4e5e38db20dbc6
Author:        Dan Carpenter <dan.carpenter@oracle.com>
AuthorDate:    Thu, 12 Mar 2020 13:56:37 +03:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 20 Mar 2020 13:06:22 +01:00

perf/core: Fix reversed NULL check in perf_event_groups_less()

This NULL check is reversed so it leads to a Smatch warning and
presumably a NULL dereference.

    kernel/events/core.c:1598 perf_event_groups_less()
    error: we previously assumed 'right->cgrp->css.cgroup' could be null
	(see line 1590)

Fixes: 95ed6c707f26 ("perf/cgroup: Order events in RB tree by cgroup id")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200312105637.GA8960@mwanda
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index b5a68d2..d22e4ba 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1586,7 +1586,7 @@ perf_event_groups_less(struct perf_event *left, struct perf_event *right)
 			 */
 			return true;
 		}
-		if (!right->cgrp || right->cgrp->css.cgroup) {
+		if (!right->cgrp || !right->cgrp->css.cgroup) {
 			/*
 			 * Right has no cgroup but left does, no cgroups come
 			 * first.