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SubjectRe: [PATCH] fs/ext{3,4}: fix potential race when setversion ioctl updates inode
On Thu, Jan 05, 2012 at 12:42:05PM +0100, Jan Kara wrote:
> On Thu 05-01-12 01:40:09, Djalal Harouni wrote:
> > Only the reiserfs and ext{2,3,4} filesystems support this ioctl. The reiserfs
> > do not use mutexes at all, even in the REISERFS_IOC_SETFLAGS ioctl which will
> > test and set _all_ the possible values of the i_flags field.
> > Perhaps I should also send a patch for this ?
> Yes, possibly reiserfs should use i_mutex for that ioctl.
For the reiserfs I've missed some locks.

It seems that reiserfs uses its own 'reiserfs_sb_info->lock' (reiserfs
super block data) to serialize writers in all the ioctl, even the GET
(readers) ioctl operations. But I also know that the VFS layer uses i_mutex
to protect inode changes, so ? I'm not sure, If I can test it I'll send a
patch.

> > And perhaps ext2 should also be updated.
> Sure. Send a patch my way when you have it.
Here's the tested ext2 patch, thanks.

--------
From: Djalal Harouni <tixxdz@opendz.org>

ext2: protect inode changes in the SETVERSION and SETFLAGS ioctls

Unlock mutex after i_flags and i_ctime updates in the EXT2_IOC_SETFLAGS
ioctl.

Use i_mutex in the EXT2_IOC_SETVERSION ioctl to protect i_ctime and
i_generation updates and make the ioctl consistent since i_mutex is
also used in other places to protect timestamps and inode changes.

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
---
fs/ext2/ioctl.c | 22 ++++++++++++++++------
1 files changed, 16 insertions(+), 6 deletions(-)
diff --git a/fs/ext2/ioctl.c b/fs/ext2/ioctl.c
index f81e250..b7f931f 100644
--- a/fs/ext2/ioctl.c
+++ b/fs/ext2/ioctl.c
@@ -77,10 +77,11 @@ long ext2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
flags = flags & EXT2_FL_USER_MODIFIABLE;
flags |= oldflags & ~EXT2_FL_USER_MODIFIABLE;
ei->i_flags = flags;
- mutex_unlock(&inode->i_mutex);

ext2_set_inode_flags(inode);
inode->i_ctime = CURRENT_TIME_SEC;
+ mutex_unlock(&inode->i_mutex);
+
mark_inode_dirty(inode);
setflags_out:
mnt_drop_write(filp->f_path.mnt);
@@ -88,20 +89,29 @@ setflags_out:
}
case EXT2_IOC_GETVERSION:
return put_user(inode->i_generation, (int __user *) arg);
- case EXT2_IOC_SETVERSION:
+ case EXT2_IOC_SETVERSION: {
+ __u32 generation;
+
if (!inode_owner_or_capable(inode))
return -EPERM;
ret = mnt_want_write(filp->f_path.mnt);
if (ret)
return ret;
- if (get_user(inode->i_generation, (int __user *) arg)) {
+ if (get_user(generation, (int __user *) arg)) {
ret = -EFAULT;
- } else {
- inode->i_ctime = CURRENT_TIME_SEC;
- mark_inode_dirty(inode);
+ goto setversion_out;
}
+
+ mutex_lock(&inode->i_mutex);
+ inode->i_ctime = CURRENT_TIME_SEC;
+ inode->i_generation = generation;
+ mutex_unlock(&inode->i_mutex);
+
+ mark_inode_dirty(inode);
+setversion_out:
mnt_drop_write(filp->f_path.mnt);
return ret;
+ }
case EXT2_IOC_GETRSVSZ:
if (test_opt(inode->i_sb, RESERVATION)
&& S_ISREG(inode->i_mode)
--
1.7.1

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