linux-kernel - Re: [PATCH] autofs: fix null deref in autofs_fill

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Message-ID: <20231114152601.GS1957730@ZenIV>
Date:   Tue, 14 Nov 2023 15:26:01 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Ian Kent <raven@...maw.net>
Cc:     Edward Adam Davis <eadavis@...com>,
        syzbot+662f87a8ef490f45fa64@...kaller.appspotmail.com,
        autofs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] autofs: fix null deref in autofs_fill_super

On Tue, Nov 14, 2023 at 04:30:25PM +0800, Ian Kent wrote:

> I'll prepare a patch, the main thing that I was concerned about was
> 
> whether the cause really was NULL root_inode but Edward more or less
> 
> tested that.

One thing: that was a massaged copy of the variant in my local tree, so
this

> > 		managed_dentry_set_managed(s->s_root);

might be worth an explanation; mainline has __managed_dentry_set_managed()
here, and yes, it is safe since nothing can access it yet, but... it's
not worth skipping on spin_lock/spin_unlock for ->d_flags update here.