fs: Add a missing permission check to do_umount



Accessing do_remount_sb should require global CAP_SYS_ADMIN, but
only one of the two call sites was appropriately protected.

Fixes CVE-2014-7975.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>

parent bfe01a5b

fs/namespace.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1356,6 +1356,8 @@ static int do_umount(struct mount *mnt, int flags)
		* Special case for "unmounting" root ...
		* we just try to remount it readonly.
		*/
		if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
		down_write(&sb->s_umount);
		if (!(sb->s_flags & MS_RDONLY))
		retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);