fs/9p: only translate RWX permissions for plain 9P2000

[ Upstream commit cd25e15e57e68a6b18dc9323047fe9c68b99290b ]

Garbage in plain 9P2000's perm bits is allowed through, which causes it
to be able to set (among others) the suid bit. This was presumably not
the intent since the unix extended bits are handled explicitly and
conditionally on .u.

Signed-off-by: Joakim Sindholt <opensource@zhasha.com>
Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index ea695c4a7a3fb13cb638e29f1b9e082df4124422..3bdf6df4b553eeb90e8fe9c82385aa89611656a4 100644 (file)
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -83,7 +83,7 @@ static int p9mode2perm(struct v9fs_session_info *v9ses,
        int res;
        int mode = stat->mode;
 
-       res = mode & S_IALLUGO;
+       res = mode & 0777; /* S_IRWXUGO */
        if (v9fs_proto_dotu(v9ses)) {
                if ((mode & P9_DMSETUID) == P9_DMSETUID)
                        res |= S_ISUID;