Re: [PATCH 16/27] r-o-bind-mounts-elevate-write-count-for-some-ioctls

Andrew Morton
2007-11-05T23:25:38Z

On Thu, 01 Nov 2007 16:08:47 -0700
Dave Hansen <haveblue@us.ibm.com> wrote:

> Some ioctl()s can cause writes to the filesystem. Take these, and make them
> use mnt_want/drop_write() instead.
>
> We need to pass the filp one layer deeper in XFS, but somebody _just_ pulled
> it out in February because nobody was using it, so I don't feel guilty for
> adding it back.

See, when we combine this patch with Jan's
forbid-user-to-change-file-flags-on-quota-files.patch we silently add bugs
to five filesystems. Lessons:

- never ever ever do `return' from deep in the guts of a function. This
is a *classic* instance of the maintainability risks which this practice
introduces.

- this whole elevate-the-write-count-in-a-zillion-places stuff is quite
fragile.

diff -puN fs/ext2/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files fs/ext2/ioctl.c
--- a/fs/ext2/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files
+++ a/fs/ext2/ioctl.c
@@ -57,7 +57,8 @@ int ext2_ioctl (struct inode * inode, st
/* Is it quota file? Do not allow user to mess with it */
if (IS_NOQUOTA(inode)) {
mutex_unlock(&inode->i_mutex);
- return -EPERM;
+ ret = -EPERM;
+ goto setflags_out;
}
oldflags = ei->i_flags;

diff -puN fs/ext3/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files fs/ext3/ioctl.c
--- a/fs/ext3/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files
+++ a/fs/ext3/ioctl.c
@@ -60,7 +60,8 @@ int ext3_ioctl (struct inode * inode, st
/* Is it quota file? Do not allow user to mess with it */
if (IS_NOQUOTA(inode)) {
mutex_unlock(&inode->i_mutex);
- return -EPERM;
+ err = -EPERM;
+ goto flags_out;
}
oldflags = ei->i_flags;

diff -puN fs/ext4/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files fs/ext4/ioctl.c
--- a/fs/ext4/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files
+++ a/fs/ext4/ioctl.c
@@ -59,7 +59,8 @@ int ext4_ioctl (struct inode * inode, st
/* Is it quota file? Do not allow user to mess with it */
if (IS_NOQUOTA(inode)) {
mutex_unlock(&inode->i_mutex);
- return -EPERM;
+ err = -EPERM;
+ goto flags_out;
}
oldflags = ei->i_flags;

diff -puN fs/jfs/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files fs/jfs/ioctl.c
--- a/fs/jfs/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files
+++ a/fs/jfs/ioctl.c
@@ -85,8 +85,10 @@ int jfs_ioctl(struct inode * inode, stru
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;
+ }
jfs_get_inode_flags(jfs_inode);
oldflags = jfs_inode->mode2;

diff -puN fs/reiserfs/ioctl.c~r-o-bind-mounts-elevate-write-count-for-some-ioctls-vs-forbid-user-to-change-file-flags-on-quota-files fs/reiserfs/ioctl.c
_