NFS: Forbid setting AF_INET6 to "struct sockaddr_in"->sin_family.

syzbot is reporting uninitialized value at rpc_sockaddr2uaddr() [1]. This
is because syzbot is setting AF_INET6 to "struct sockaddr_in"->sin_family
(which is embedded into user-visible "struct nfs_mount_data" structure)
despite nfs23_validate_mount_data() cannot pass sizeof(struct sockaddr_in6)
bytes of AF_INET6 address to rpc_sockaddr2uaddr().

Since "struct nfs_mount_data" structure is user-visible, we can't change
"struct nfs_mount_data" to use "struct sockaddr_storage". Therefore,
assuming that everybody is using AF_INET family when passing address via
"struct nfs_mount_data"->addr, reject if its sin_family is not AF_INET.

[1] https://syzkaller.appspot.com/bug?id=599993614e7cbbf66bc2656a919ab2a95fb5d75c

Reported-by: syzbot <syzbot+047a11c361b872896a4f@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 23790c7b2289d21328db2a824eef5c6484e29089..c27ac96a95bd3535bc893493492fdc7681aba1fe 100644 (file)
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2041,7 +2041,8 @@ static int nfs23_validate_mount_data(void *options,
                memcpy(sap, &data->addr, sizeof(data->addr));
                args->nfs_server.addrlen = sizeof(data->addr);
                args->nfs_server.port = ntohs(data->addr.sin_port);
-               if (!nfs_verify_server_address(sap))
+               if (sap->sa_family != AF_INET ||
+                   !nfs_verify_server_address(sap))
                        goto out_no_address;
 
                if (!(data->flags & NFS_MOUNT_TCP))