linux-kernel - [PATCH 2.6.32 10/38] [PATCH 10/38] rds: fix an integer overflow test in rds_info

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Message-Id: <20151129214703.302706599@1wt.eu>
Date:	Sun, 29 Nov 2015 22:47:12 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Ben Hutchings <ben@...adent.org.uk>, Willy Tarreau <w@....eu>
Subject: [PATCH 2.6.32 10/38] [PATCH 10/38] rds: fix an integer overflow test in
 rds_info_getsockopt()

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

commit 468b732b6f76b138c0926eadf38ac88467dcd271 upstream.

"len" is a signed integer.  We check that len is not negative, so it
goes from zero to INT_MAX.  PAGE_SIZE is unsigned long so the comparison
is type promoted to unsigned long.  ULONG_MAX - 4095 is a higher than
INT_MAX so the condition can never be true.

I don't know if this is harmful but it seems safe to limit "len" to
INT_MAX - 4095.

Fixes: a8c879a7ee98 ('RDS: Info and stats')
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
(cherry picked from commit f3a66bdc88c3261f55b942453476e623056b92d9)
Signed-off-by: Willy Tarreau <w@....eu>
---
 net/rds/info.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/info.c b/net/rds/info.c
index 814a91a..0a857a0 100644
--- a/net/rds/info.c
+++ b/net/rds/info.c
@@ -174,7 +174,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
 
 	/* check for all kinds of wrapping and the like */
 	start = (unsigned long)optval;
-	if (len < 0 || len + PAGE_SIZE - 1 < len || start + len < start) {
+	if (len < 0 || len > INT_MAX - PAGE_SIZE + 1 || start + len < start) {
 		ret = -EINVAL;
 		goto out;
 	}
-- 
1.7.12.2.21.g234cd45.dirty



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