[PATCH] r/o bind mounts: elevate write count for ioctls()

Some ioctl()s can cause writes to the filesystem.  Take these, and make them
use mnt_want/drop_write() instead.

[AV: updated]

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 6 insertions, 5 deletions

diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c
index b413166dd163..7b142f0ce995 100644
--- a/fs/ocfs2/ioctl.c
+++ b/fs/ocfs2/ioctl.c
@@ -60,10 +60,6 @@ static int ocfs2_set_inode_attr(struct inode *inode, unsigned flags,
                 goto bail;
         }
 
-        status = -EROFS;
-        if (IS_RDONLY(inode))
-                goto bail_unlock;
-
         status = -EACCES;
         if (!is_owner_or_cap(inode))
                 goto bail_unlock;
@@ -134,8 +130,13 @@ long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                 if (get_user(flags, (int __user *) arg))
                         return -EFAULT;
 
-                return ocfs2_set_inode_attr(inode, flags,
+                status = mnt_want_write(filp->f_path.mnt);
+                if (status)
+                        return status;
+                status = ocfs2_set_inode_attr(inode, flags,
                         OCFS2_FL_MODIFIABLE);
+                mnt_drop_write(filp->f_path.mnt);
+                return status;
         case OCFS2_IOC_RESVSP:
         case OCFS2_IOC_RESVSP64:
         case OCFS2_IOC_UNRESVSP: