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	Fri, 04 Apr 2025 08:47:12 +0000
Date: Fri, 4 Apr 2025 01:47:12 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	Penglei Jiang <superman.xpt@gmail.com>, viro@zeniv.linux.org.uk,
	jack@suse.cz, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	syzbot+5d8e79d323a13aa0b248@syzkaller.appspotmail.com
Subject: Re: [PATCH 2/2] vfs: Fix anon_inode triggering VFS_BUG_ON_INODE in
 may_open()
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References: <20250403015946.5283-1-superman.xpt@gmail.com>
 <Z--Y_pEL9NAXWloL@infradead.org>
 <20250404-kammer-fahrrad-516fe910491e@brauner>
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On Fri, Apr 04, 2025 at 10:45:43AM +0200, Christian Brauner wrote:
> On Fri, Apr 04, 2025 at 01:31:58AM -0700, Christoph Hellwig wrote:
> > Please make sure anon inodes have a valid mode set.  Leaving this
> > landmine around where we have inodes without a valid mode is just going
> > to create more problems in the future.
> 
> We've tried to change it, it immediately leads to userspace tools
> regressions as they've started to rely on that behavior because it's been
> like that since the dawn of time. We even had to work around that crap
> in pidfs because lsof regressed. So now, we can't do this.

Just because i_mode has something useful, we don't need to report that
to userspace.  We can still clear kstat.mode (with a big fat comment
explaining why).