Re: [syzbot] [fs?] WARNING in stashed_dentry_prune

[Hillf Danton <hdanton@sina.com>]

On Wed, 13 Mar 2024 03:23:25 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    0f1a876682f0 Merge tag 'vfs-6.9.uuid' of git://git.kernel...
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=116b38d1180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master

--- x/fs/libfs.c
+++ y/fs/libfs.c
@@ -2012,6 +2012,8 @@ static struct dentry *prepare_anon_dentr
 	dentry = d_alloc_anon(sb);
 	if (!dentry)
 		return ERR_PTR(-ENOMEM);
+	/* Store address of location where dentry's supposed to be stashed. */
+	dentry->d_fsdata = stashed;
 
 	inode = new_inode_pseudo(sb);
 	if (!inode) {
@@ -2029,9 +2031,6 @@ static struct dentry *prepare_anon_dentr
 	WARN_ON_ONCE(!S_ISREG(inode->i_mode));
 	WARN_ON_ONCE(!IS_IMMUTABLE(inode));
 
-	/* Store address of location where dentry's supposed to be stashed. */
-	dentry->d_fsdata = stashed;
-
 	/* @data is now owned by the fs */
 	d_instantiate(dentry, inode);
 	return dentry;
--