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From: Al Viro <viro@zeniv.linux.org.uk>
To: Hillf Danton <hdanton@sina.com>
Cc: syzbot <syzbot+75867c44841cb6373570@syzkaller.appspotmail.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	syzkaller-bugs@googlegroups.com,
	Markus Elfring <Markus.Elfring@web.de>
Subject: Re: KASAN: use-after-free Read in userfaultfd_release (2)
Date: Mon, 20 Jul 2020 17:00:59 +0100	[thread overview]
Message-ID: <20200720160059.GO2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200713084512.10416-1-hdanton@sina.com>

On Mon, Jul 13, 2020 at 04:45:12PM +0800, Hillf Danton wrote:

> Bridge the gap between slab free and the fput in task work wrt
> file's private data.

No.  This

> @@ -2048,6 +2055,7 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
>  
>  	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
>  	if (fd < 0) {
> +		file->private_data = NULL;
>  		fput(file);
>  		goto out;
>  	}
> 

is fundamentally wrong; you really shouldn't take over the cleanups
if you ever do fput().

  parent reply	other threads:[~2020-07-20 16:01 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-13  2:24 syzbot
2020-07-13 15:34 ` syzbot
2020-07-17 15:05   ` Qian Cai
2020-07-20 15:50     ` Qian Cai
2020-07-21  4:32       ` Stephen Rothwell
     [not found] ` <20200713084512.10416-1-hdanton@sina.com>
2020-07-20 16:00   ` Al Viro [this message]
2020-07-20 23:46     ` Daniel Colascione

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