diff options
| author | Miklos Szeredi <mszeredi@suse.cz> | 2010-02-10 12:15:53 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-07-05 11:16:09 -0700 |
| commit | 7ab3c6bcc33237784b5dd8ef86062d488fd65576 (patch) | |
| tree | c1c7d87f17740de1d82fc19a15583746afdfdd27 | |
| parent | 8c11d9038537657cc74fb8d2242fd18c3d6a05d5 (diff) | |
vfs: add NOFOLLOW flag to umount(2)
commit db1f05bb85d7966b9176e293f3ceead1cb8b5d79 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -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 c768f733c8d..bf6b6febc7e 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1121,8 +1121,15 @@ 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 81288f0d717..899a4d6985d 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1308,6 +1308,8 @@ 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; |