[PATCH 1/1] net: clamp ->msg_namelen instead of returning an error

[Andy Whitcroft]

From: Dan Carpenter <dan.carpenter at oracle.com>

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 at yhbt.net>
Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
Tested-by: Eric Wong <normalperson at yhbt.net>
Acked-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>

(cherry picked from commit db31c55a6fb245fdbb752a2ca4aefec89afabb06)
BugLink: http://bugs.launchpad.net/bugs/1269053
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 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 8903258..09c3d84 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);
diff --git a/net/socket.c b/net/socket.c
index 4b94643..d64bfbf 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1979,7 +1979,7 @@ 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;
 }
 
-- 
1.8.5.2