diff options
| author | Valerie Aurora <vaurora@redhat.com> | 2010-08-26 11:07:22 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-09-07 13:46:20 -0700 |
| commit | 7a2e8a8faab76386d8eaae9ded739ee5615be174 (patch) | |
| tree | 404b9c185f32e3e6ef871bb85c217314e4aff3e8 /fs | |
| parent | 2bfc96a127bc1cc94d26bfaa40159966064f9c8c (diff) | |
VFS: Sanity check mount flags passed to change_mnt_propagation()
Sanity check the flags passed to change_mnt_propagation(). Exactly
one flag should be set. Return EINVAL otherwise.
Userspace can pass in arbitrary combinations of MS_* flags to mount().
do_change_type() is called if any of MS_SHARED, MS_PRIVATE, MS_SLAVE,
or MS_UNBINDABLE is set. do_change_type() clears MS_REC and then
calls change_mnt_propagation() with the rest of the user-supplied
flags. change_mnt_propagation() clearly assumes only one flag is set
but do_change_type() does not check that this is true. For example,
mount() with flags MS_SHARED | MS_RDONLY does not actually make the
mount shared or read-only but does clear MNT_UNBINDABLE.
Signed-off-by: Valerie Aurora <vaurora@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/namespace.c | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index de402eb6eafb..a72eaabfe8f2 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1484,13 +1484,30 @@ out_unlock: } /* + * Sanity check the flags to change_mnt_propagation. + */ + +static int flags_to_propagation_type(int flags) +{ + int type = flags & ~MS_REC; + + /* Fail if any non-propagation flags are set */ + if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) + return 0; + /* Only one propagation flag should be set */ + if (!is_power_of_2(type)) + return 0; + return type; +} + +/* * recursively change the type of the mountpoint. */ static int do_change_type(struct path *path, int flag) { struct vfsmount *m, *mnt = path->mnt; int recurse = flag & MS_REC; - int type = flag & ~MS_REC; + int type; int err = 0; if (!capable(CAP_SYS_ADMIN)) @@ -1499,6 +1516,10 @@ static int do_change_type(struct path *path, int flag) if (path->dentry != path->mnt->mnt_root) return -EINVAL; + type = flags_to_propagation_type(flag); + if (!type) + return -EINVAL; + down_write(&namespace_sem); if (type == MS_SHARED) { err = invent_group_ids(mnt, recurse); |