From: Christoph Hellwig <hch@lst.de>
Date: Mon, 19 Jan 2009 01:03:03 +0000 (+0100)
Subject: xfs: use mnt_want_write in compat_attrmulti ioctl
X-Git-Tag: v2.6.29-rc3~44^2~7
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=62e194ecdaf8a1935991c1f8704886328d96a391;p=linux-2.6-omap-h63xx.git

xfs: use mnt_want_write in compat_attrmulti ioctl

The compat version of the attrmulti ioctl needs to ask for and then
later release write access to the mount just like the native version,
otherwise we could potentially write to read-only mounts.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>
---

diff --git a/fs/xfs/linux-2.6/xfs_ioctl32.c b/fs/xfs/linux-2.6/xfs_ioctl32.c
index fd4362063f2..c70c4e3db79 100644
--- a/fs/xfs/linux-2.6/xfs_ioctl32.c
+++ b/fs/xfs/linux-2.6/xfs_ioctl32.c
@@ -17,6 +17,7 @@
  */
 #include <linux/compat.h>
 #include <linux/ioctl.h>
+#include <linux/mount.h>
 #include <asm/uaccess.h>
 #include "xfs.h"
 #include "xfs_fs.h"
@@ -458,15 +459,23 @@ xfs_compat_attrmulti_by_handle(
 					&ops[i].am_length, ops[i].am_flags);
 			break;
 		case ATTR_OP_SET:
+			ops[i].am_error = mnt_want_write(parfilp->f_path.mnt);
+			if (ops[i].am_error)
+				break;
 			ops[i].am_error = xfs_attrmulti_attr_set(
 					dentry->d_inode, attr_name,
 					compat_ptr(ops[i].am_attrvalue),
 					ops[i].am_length, ops[i].am_flags);
+			mnt_drop_write(parfilp->f_path.mnt);
 			break;
 		case ATTR_OP_REMOVE:
+			ops[i].am_error = mnt_want_write(parfilp->f_path.mnt);
+			if (ops[i].am_error)
+				break;
 			ops[i].am_error = xfs_attrmulti_attr_remove(
 					dentry->d_inode, attr_name,
 					ops[i].am_flags);
+			mnt_drop_write(parfilp->f_path.mnt);
 			break;
 		default:
 			ops[i].am_error = EINVAL;