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Date: Sat, 24 Nov 2018 19:51:17 +0000
From: Al Viro <viro@zeniv.linux.org.uk>
To: Pan Bian <bianpan2016@163.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] namei: free new_dentry late
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On Sat, Nov 24, 2018 at 05:23:24PM +0800, Pan Bian wrote:
> After calling dput(new_dentry), new_dentry is passed to fsnotify_move.
> This may result in a use-after-free bug. This patch moves the put
> operation late.
>
> Fixes: 49d31c2f389a("dentry name snapshots")

What does that commit have to do with anything?  The broken part is
                        fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
                                      new_is_dir, NULL, new_dentry);
and it predates that commit by 3 years - it came from da1ce0670c14 ("vfs: add
cross-rename")...