[3.11.y.z extended stable] Patch "xfs: add capability check to free eofblocks ioctl" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    xfs: add capability check to free eofblocks ioctl

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 45370570966b668f98788b51d9ab8de9a437e6cd Mon Sep 17 00:00:00 2001
From: Dwight Engen <dwight.engen at oracle.com>
Date: Thu, 15 Aug 2013 14:08:03 -0400
Subject: xfs: add capability check to free eofblocks ioctl

commit 8c567a7fab6e086a0284eee2db82348521e7120c upstream.

Check for CAP_SYS_ADMIN since the caller can truncate preallocated
blocks from files they do not own nor have write access to. A more
fine grained access check was considered: require the caller to
specify their own uid/gid and to use inode_permission to check for
write, but this would not catch the case of an inode not reachable
via path traversal from the callers mount namespace.

Add check for read-only filesystem to free eofblocks ioctl.

Reviewed-by: Brian Foster <bfoster at redhat.com>
Reviewed-by: Dave Chinner <dchinner at redhat.com>
Reviewed-by: Gao feng <gaofeng at cn.fujitsu.com>
Signed-off-by: Dwight Engen <dwight.engen at oracle.com>
Signed-off-by: Ben Myers <bpm at sgi.com>
Cc: Kees Cook <keescook at google.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/xfs/xfs_ioctl.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 6e2bca5..bccd2a3 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1612,6 +1612,12 @@ xfs_file_ioctl(
 	case XFS_IOC_FREE_EOFBLOCKS: {
 		struct xfs_eofblocks eofb;

+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+
+		if (mp->m_flags & XFS_MOUNT_RDONLY)
+			return -XFS_ERROR(EROFS);
+
 		if (copy_from_user(&eofb, arg, sizeof(eofb)))
 			return -XFS_ERROR(EFAULT);

--
1.8.3.2