netdev - [patch] net: clamp ->msg_namelen instead of returning an error

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Message-ID: <20131127124021.GA2025@elgon.mountain>
Date:	Wed, 27 Nov 2013 15:40:21 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, Eric Wong <normalperson@...t.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: [patch] net: clamp ->msg_namelen instead of returning an error

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.

Reported-by: Eric Wong <normalperson@...t.net>
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/net/socket.c b/net/socket.c
index 0b18693f2be6..e83c416708af 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1973,7 +1973,7 @@ 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;
 }
 
diff --git a/net/compat.c b/net/compat.c
index 618c6a8a911b..dd32e34c1e2c 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -72,7 +72,7 @@ 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);
--
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