From: Andy Lutomirski <luto@amacapital.net>
Date: Wed, 8 Oct 2014 19:32:47 +0000 (-0700)
Subject: fs: Add a missing permission check to do_umount
X-Git-Tag: v3.17.2~133
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=28f64f916f0d70e65f6744e41329815c3805f9c5;p=people%2Fms%2Flinux.git

fs: Add a missing permission check to do_umount

commit a1480dcc3c706e309a88884723446f2e84fedd5b upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index ef42d9bee212..7f67b463a5b4 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -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);