netdev - [PATCH v2] ipv4: fib_rules: Fix possible infinite loop in fib_empty

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Message-ID: <20181229064523.15812-1-yuehaibing@huawei.com>
Date:   Sat, 29 Dec 2018 14:45:23 +0800
From:   YueHaibing <yuehaibing@...wei.com>
To:     <davem@...emloft.net>, <kuznet@....inr.ac.ru>,
        <yoshfuji@...ux-ipv6.org>
CC:     <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        YueHaibing <yuehaibing@...wei.com>
Subject: [PATCH v2] ipv4: fib_rules: Fix possible infinite loop in fib_empty_table

gcc warn this:
net/ipv4/fib_rules.c:203 fib_empty_table() warn:
 always true condition '(id <= 4294967295) => (0-u32max <= u32max)'

'id' is u32, which always not greater than RT_TABLE_MAX
(0xFFFFFFFF), So add a check to break while wrap around.

Signed-off-by: YueHaibing <yuehaibing@...wei.com>
---
v2: clean up exit conditions
---
 net/ipv4/fib_rules.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/fib_rules.c b/net/ipv4/fib_rules.c
index f8eb78d..cfec3af 100644
--- a/net/ipv4/fib_rules.c
+++ b/net/ipv4/fib_rules.c
@@ -198,11 +198,15 @@ static int fib4_rule_match(struct fib_rule *rule, struct flowi *fl, int flags)
 
 static struct fib_table *fib_empty_table(struct net *net)
 {
-	u32 id;
+	u32 id = 1;
 
-	for (id = 1; id <= RT_TABLE_MAX; id++)
+	while (1) {
 		if (!fib_get_table(net, id))
 			return fib_new_table(net, id);
+
+		if (id++ == RT_TABLE_MAX)
+			break;
+	}
 	return NULL;
 }
 
-- 
2.7.4