linux-kernel - [ 083/143] net: clamp ->msg_namelen instead of returning an error

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Date:	Mon, 12 May 2014 02:33:23 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu>
Subject: [ 083/143] net: clamp ->msg_namelen instead of returning an error

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

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

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit db31c55a6fb245fdbb752a2ca4aefec89afabb06 ]

If kmsg->msg_namelen > sizeof(struct sockaddr_storage) then in the
original code that would lead to memory corruption in the kernel if you
had audit configured.  If you didn't have audit configured it was
harmless.

There are some programs such as beta versions of Ruby which use too
large of a buffer and returning an error code breaks them.  We should
clamp the ->msg_namelen value instead.

Fixes: 1661bf364ae9 ("net: heap overflow in __audit_sockaddr()")
Reported-by: Eric Wong <normalperson@...t.net>
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Tested-by: Eric Wong <normalperson@...t.net>
Acked-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Willy Tarreau <w@....eu>
---
 net/compat.c | 2 +-
 net/socket.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/compat.c b/net/compat.c
index d325d16..e9672c8 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -70,7 +70,7 @@ int get_compat_msghdr(struct msghdr *kmsg, struct compat_msghdr __user *umsg)
 	    __get_user(kmsg->msg_flags, &umsg->msg_flags))
 		return -EFAULT;
 	if (kmsg->msg_namelen > sizeof(struct sockaddr_storage))
-		return -EINVAL;
+		kmsg->msg_namelen = sizeof(struct sockaddr_storage);
 	kmsg->msg_name = compat_ptr(tmp1);
 	kmsg->msg_iov = compat_ptr(tmp2);
 	kmsg->msg_control = compat_ptr(tmp3);
diff --git a/net/socket.c b/net/socket.c
index 712f977..0823497 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1872,7 +1872,7 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
 	if (copy_from_user(kmsg, umsg, sizeof(struct msghdr)))
 		return -EFAULT;
 	if (kmsg->msg_namelen > sizeof(struct sockaddr_storage))
-		return -EINVAL;
+		kmsg->msg_namelen = sizeof(struct sockaddr_storage);
 	return 0;
 }
 
-- 
1.7.12.2.21.g234cd45.dirty



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