[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, 22 insertions, 11 deletions

diff --git a/fs/jfs/ioctl.c b/fs/jfs/ioctl.c
index a1f8e375ad21..afe222bf300f 100644
--- a/fs/jfs/ioctl.c
+++ b/fs/jfs/ioctl.c
@@ -8,6 +8,7 @@
 #include <linux/fs.h>
 #include <linux/ctype.h>
 #include <linux/capability.h>
+#include <linux/mount.h>
 #include <linux/time.h>
 #include <linux/sched.h>
 #include <asm/current.h>
@@ -65,23 +66,30 @@ long jfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                 return put_user(flags, (int __user *) arg);
         case JFS_IOC_SETFLAGS: {
                 unsigned int oldflags;
+                int err;
 
-                if (IS_RDONLY(inode))
-                        return -EROFS;
+                err = mnt_want_write(filp->f_path.mnt);
+                if (err)
+                        return err;
 
-                if (!is_owner_or_cap(inode))
-                        return -EACCES;
-
-                if (get_user(flags, (int __user *) arg))
-                        return -EFAULT;
+                if (!is_owner_or_cap(inode)) {
+                        err = -EACCES;
+                        goto setflags_out;
+                }
+                if (get_user(flags, (int __user *) arg)) {
+                        err = -EFAULT;
+                        goto setflags_out;
+                }
 
                 flags = jfs_map_ext2(flags, 1);
                 if (!S_ISDIR(inode->i_mode))
                         flags &= ~JFS_DIRSYNC_FL;
 
                 /* Is it quota file? Do not allow user to mess with it */
-                if (IS_NOQUOTA(inode))
-                        return -EPERM;
+                if (IS_NOQUOTA(inode)) {
+                        err = -EPERM;
+                        goto setflags_out;
+                }
 
                 /* Lock against other parallel changes of flags */
                 mutex_lock(&inode->i_mutex);
@@ -98,7 +106,8 @@ long jfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                         (JFS_APPEND_FL | JFS_IMMUTABLE_FL))) {
                         if (!capable(CAP_LINUX_IMMUTABLE)) {
                                 mutex_unlock(&inode->i_mutex);
-                                return -EPERM;
+                                err = -EPERM;
+                                goto setflags_out;
                         }
                 }
 
@@ -110,7 +119,9 @@ long jfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                 mutex_unlock(&inode->i_mutex);
                 inode->i_ctime = CURRENT_TIME_SEC;
                 mark_inode_dirty(inode);
-                return 0;
+setflags_out:
+                mnt_drop_write(filp->f_path.mnt);
+                return err;
         }
         default:
                 return -ENOTTY;