linux-kernel - [PATCH v1] net: ipv6: fix racey clock check in route cache aging logic

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Message-Id: <20181025211352.112096-1-brendanhiggins@google.com>
Date:   Thu, 25 Oct 2018 14:13:52 -0700
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Brendan Higgins <brendanhiggins@...gle.com>
Subject: [PATCH v1] net: ipv6: fix racey clock check in route cache aging logic

Fix a bug where, with certain settings, the aging logic does not use the
time passed in as the current time, but instead directly checks jiffies.

This bug can be reproduced with (and this fix verified with) the test
at: https://kunit-review.googlesource.com/c/linux/+/1156

Fixes: 31afeb425f7f ("ipv6: change route cache aging logic")
Discovered-by-KUnit: https://kunit-review.googlesource.com/c/linux/+/1156
Signed-off-by: Brendan Higgins <brendanhiggins@...gle.com>
---
 net/ipv6/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 2a7423c394560..54d28b91fd840 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1734,7 +1734,7 @@ static void rt6_age_examine_exception(struct rt6_exception_bucket *bucket,
 			rt6_remove_exception(bucket, rt6_ex);
 			return;
 		}
-	} else if (time_after(jiffies, rt->dst.expires)) {
+	} else if (time_after(now, rt->dst.expires)) {
 		RT6_TRACE("purging expired route %p\n", rt);
 		rt6_remove_exception(bucket, rt6_ex);
 		return;
-- 
2.19.1.568.g152ad8e336-goog