[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, 25 insertions, 15 deletions

diff --git a/fs/hfsplus/ioctl.c b/fs/hfsplus/ioctl.c
index b60c0affbec5..f457d2ca51ab 100644
--- a/fs/hfsplus/ioctl.c
+++ b/fs/hfsplus/ioctl.c
@@ -14,6 +14,7 @@
 
 #include <linux/capability.h>
 #include <linux/fs.h>
+#include <linux/mount.h>
 #include <linux/sched.h>
 #include <linux/xattr.h>
 #include <asm/uaccess.h>
@@ -35,25 +36,32 @@ int hfsplus_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
                         flags |= FS_NODUMP_FL; /* EXT2_NODUMP_FL */
                 return put_user(flags, (int __user *)arg);
         case HFSPLUS_IOC_EXT2_SETFLAGS: {
-                if (IS_RDONLY(inode))
-                        return -EROFS;
-
-                if (!is_owner_or_cap(inode))
-                        return -EACCES;
-
-                if (get_user(flags, (int __user *)arg))
-                        return -EFAULT;
-
+                int err = 0;
+                err = mnt_want_write(filp->f_path.mnt);
+                if (err)
+                        return err;
+
+                if (!is_owner_or_cap(inode)) {
+                        err = -EACCES;
+                        goto setflags_out;
+                }
+                if (get_user(flags, (int __user *)arg)) {
+                        err = -EFAULT;
+                        goto setflags_out;
+                }
                 if (flags & (FS_IMMUTABLE_FL|FS_APPEND_FL) ||
                     HFSPLUS_I(inode).rootflags & (HFSPLUS_FLG_IMMUTABLE|HFSPLUS_FLG_APPEND)) {
-                        if (!capable(CAP_LINUX_IMMUTABLE))
-                                return -EPERM;
+                        if (!capable(CAP_LINUX_IMMUTABLE)) {
+                                err = -EPERM;
+                                goto setflags_out;
+                        }
                 }
 
                 /* don't silently ignore unsupported ext2 flags */
-                if (flags & ~(FS_IMMUTABLE_FL|FS_APPEND_FL|FS_NODUMP_FL))
-                        return -EOPNOTSUPP;
-
+                if (flags & ~(FS_IMMUTABLE_FL|FS_APPEND_FL|FS_NODUMP_FL)) {
+                        err = -EOPNOTSUPP;
+                        goto setflags_out;
+                }
                 if (flags & FS_IMMUTABLE_FL) { /* EXT2_IMMUTABLE_FL */
                         inode->i_flags |= S_IMMUTABLE;
                         HFSPLUS_I(inode).rootflags |= HFSPLUS_FLG_IMMUTABLE;
@@ -75,7 +83,9 @@ int hfsplus_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
 
                 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;