From 7a2e8a8faab76386d8eaae9ded739ee5615be174 Mon Sep 17 00:00:00 2001 From: Valerie Aurora Date: Thu, 26 Aug 2010 11:07:22 -0700 Subject: [PATCH] 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 Signed-off-by: Linus Torvalds --- fs/namespace.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/fs/namespace.c b/fs/namespace.c index de402eb6eafb..a72eaabfe8f2 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1483,6 +1483,23 @@ static int graft_tree(struct vfsmount *mnt, struct path *path) return err; } +/* + * 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. */ @@ -1490,7 +1507,7 @@ 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); -- GitLab