From db1f05bb85d7966b9176e293f3ceead1cb8b5d79 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 10 Feb 2010 12:15:53 +0100 Subject: vfs: add NOFOLLOW flag to umount(2) Add a new UMOUNT_NOFOLLOW flag to umount(2). This is needed to prevent symlink attacks in unprivileged unmounts (fuse, samba, ncpfs). Additionally, return -EINVAL if an unknown flag is used (and specify an explicitly unused flag: UMOUNT_UNUSED). This makes it possible for the caller to determine if a flag is supported or not. CC: Eugene Teo CC: Michael Kerrisk Signed-off-by: Miklos Szeredi Signed-off-by: Al Viro --- fs/namespace.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'fs/namespace.c') diff --git a/fs/namespace.c b/fs/namespace.c index ffa3843404e0..8174c8ab5c70 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1136,8 +1136,15 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags) { struct path path; int retval; + int lookup_flags = 0; - retval = user_path(name, &path); + if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) + return -EINVAL; + + if (!(flags & UMOUNT_NOFOLLOW)) + lookup_flags |= LOOKUP_FOLLOW; + + retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); if (retval) goto out; retval = -EINVAL; -- cgit v1.2.3