linux-kernel - Re: Linux 3.2-rc6

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Date:	Sat, 17 Dec 2011 08:49:44 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Chris Mason <chris.mason@...cle.com>,
	Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: Linux 3.2-rc6

On Fri, Dec 16, 2011 at 06:53:17PM -0800, Linus Torvalds wrote:

> Casey Schaufler (1):
>       BTRFS: Establish i_ops before calling d_instantiate

I'm sorry, but that's nowhere near enough.  As I said in followup to
the original posting of that patch, it still leaves a race window
where inode is already associated with dentry but still doesn't have
->a_ops, etc. set up.  Hell, ->symlink() doesn't write the symlink
body until after that point...

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 329a5c6..d9501f5 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4590,10 +4590,6 @@ static int btrfs_add_nondir(struct btrfs_trans_handle *trans,
 	int err = btrfs_add_link(trans, dir, inode,
 				 dentry->d_name.name, dentry->d_name.len,
 				 backref, index);
-	if (!err) {
-		d_instantiate(dentry, inode);
-		return 0;
-	}
 	if (err > 0)
 		err = -EEXIST;
 	return err;
@@ -4655,6 +4651,7 @@ static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
 	else {
 		init_special_inode(inode, inode->i_mode, rdev);
 		btrfs_update_inode(trans, root, inode);
+		d_instantiate(dentry, inode);
 	}
 out_unlock:
 	nr = trans->blocks_used;
@@ -4722,6 +4719,7 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
 		inode->i_mapping->a_ops = &btrfs_aops;
 		inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
 		BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
+		d_instantiate(dentry, inode);
 	}
 out_unlock:
 	nr = trans->blocks_used;
@@ -4780,6 +4778,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
 		err = btrfs_update_inode(trans, root, inode);
 		BUG_ON(err);
 		btrfs_log_new_name(trans, inode, NULL, parent);
+		d_instantiate(dentry, inode);
 	}
 
 	nr = trans->blocks_used;
@@ -7244,6 +7243,8 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
 		drop_inode = 1;
 
 out_unlock:
+	if (!err)
+		d_instantiate(dentry, inode);
 	nr = trans->blocks_used;
 	btrfs_end_transaction_throttle(trans, root);
 	if (drop_inode) {
--
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