linux-kernel - Re: [PATCH] fs: Prevent non-symlinks from entering pick link

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Message-ID: <tencent_9DDC9378E363A961A3BEA440376237718605@qq.com>
Date: Wed, 18 Jun 2025 13:34:18 +0800
From: Edward Adam Davis <eadavis@...com>
To: viro@...iv.linux.org.uk
Cc: almaz.alexandrovich@...agon-software.com,
	brauner@...nel.org,
	eadavis@...com,
	jack@...e.cz,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	ntfs3@...ts.linux.dev,
	syzbot+1aa90f0eb1fc3e77d969@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] fs: Prevent non-symlinks from entering pick link

On Wed, 18 Jun 2025 06:27:47 +0100, Al Viro wrote:
> Note that anything that calls __d_add(dentry, inode) with is_bad_inode(inode)
> (or d_add(), or d_instantiate(), or d_splice_alias() under the same conditions)
> is also FUBAR.
> 
> So's anything that calls make_bad_inode() on a struct inode that might be
> in process of being passed to one of those functions by another thread.
> 
> This is fundamentally wrong; bad inodes are not supposed to end up attached
> to dentries.
As far as I know, pick_link() is used to resolve the target path of a
symbolic link (symlink). Can you explain why pick_link() is executed on
a directory or a regular file?