diff options
| author | Miklos Szeredi <mszeredi@suse.cz> | 2010-02-10 12:15:53 +0100 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2010-03-03 14:08:00 -0500 |
| commit | db1f05bb85d7966b9176e293f3ceead1cb8b5d79 (patch) | |
| tree | 65a1d746f84cb8aa9be2a69c59eb627859b9fa0d | |
| parent | 440b3c6c160f7d0a985f24ad1f4c24e00ee2d936 (diff) | |
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 <eugene@redhat.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -rw-r--r-- | fs/namespace.c | 9 | ||||
| -rw-r--r-- | include/linux/fs.h | 2 |
2 files changed, 10 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index ffa3843404e..8174c8ab5c7 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; diff --git a/include/linux/fs.h b/include/linux/fs.h index e764f247d0a..5b3182c7eb5 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1305,6 +1305,8 @@ extern int send_sigurg(struct fown_struct *fown); #define MNT_FORCE 0x00000001 /* Attempt to forcibily umount */ #define MNT_DETACH 0x00000002 /* Just detach from the tree */ #define MNT_EXPIRE 0x00000004 /* Mark for expiry */ +#define UMOUNT_NOFOLLOW 0x00000008 /* Don't follow symlink on umount */ +#define UMOUNT_UNUSED 0x80000000 /* Flag guaranteed to be unused */ extern struct list_head super_blocks; extern spinlock_t sb_lock; |