From: Eric Biggers <ebiggers@google.com>
Date: Fri, 30 Dec 2016 23:42:32 +0000 (-0600)
Subject: net: socket: don't set sk_uid to garbage value in ->setattr()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e1a3a60a2ebe991605acb14cd58e39c0545e174e;p=linux.git

net: socket: don't set sk_uid to garbage value in ->setattr()

->setattr() was recently implemented for socket files to sync the socket
inode's uid to the new 'sk_uid' member of struct sock.  It does this by
copying over the ia_uid member of struct iattr.  However, ia_uid is
actually only valid when ATTR_UID is set in ia_valid, indicating that
the uid is being changed, e.g. by chown.  Other metadata operations such
as chmod or utimes leave ia_uid uninitialized.  Therefore, sk_uid could
be set to a "garbage" value from the stack.

Fix this by only copying the uid over when ATTR_UID is set.

Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Tested-by: Lorenzo Colitti <lorenzo@google.com>
Acked-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/socket.c b/net/socket.c
index 8487bf136e5c4..a8c2307590b87 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -537,7 +537,7 @@ int sockfs_setattr(struct dentry *dentry, struct iattr *iattr)
 {
 	int err = simple_setattr(dentry, iattr);
 
-	if (!err) {
+	if (!err && (iattr->ia_valid & ATTR_UID)) {
 		struct socket *sock = SOCKET_I(d_inode(dentry));
 
 		sock->sk->sk_uid = iattr->ia_uid;