netdev - [PATCH] ipv6: fix signedness of tmp_prefered

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Date:   Tue, 18 Oct 2016 17:01:54 +0200
From:   Jiri Bohac <jbohac@...e.cz>
To:     Julia Lawall <julia.lawall@...6.fr>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>
Cc:     netdev@...r.kernel.org, kbuild-all@...org
Subject: [PATCH] ipv6: fix signedness of tmp_prefered_lft underflow check

Commit 76506a986dc31394fd1f2741db037d29c7e57843 (IPv6: fix
DESYNC_FACTOR) introduced a buggy check for underflow of
tmp_prefered_lft. tmp_prefered_lft is unsigned, so the condition
is always false.

Signed-off-by: Jiri Bohac <jbohac@...e.cz>
Reported-by: Julia Lawall <julia.lawall@...6.fr>
Fixes: 76506a986dc3 ("IPv6: fix DESYNC_FACTOR")

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index cc7c26d..7a043a4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1248,7 +1248,7 @@ static int ipv6_create_tempaddr(struct inet6_ifaddr *ifp, struct inet6_ifaddr *i
 	tmp_prefered_lft = idev->cnf.temp_prefered_lft + age -
 			    idev->desync_factor;
 	/* guard against underflow in case of concurrent updates to cnf */
-	if (unlikely(tmp_prefered_lft < 0))
+	if (unlikely((long)tmp_prefered_lft < 0))
 		tmp_prefered_lft = 0;
 	tmp_prefered_lft = min_t(__u32, ifp->prefered_lft, tmp_prefered_lft);
 	tmp_plen = ifp->prefix_len;