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 7d42f0c6c644ffdf8b1441bcf8202d478a249d09..ae3623bc4ef4633464c207c624a4b66c8040cd0b 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;