From: Daniel Colascione <dancol@dancol.org>
To: Al Viro <viro@zeniv.linux.org.uk>, 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 16:46:00 -0700 [thread overview]
Message-ID: <1f69c0ab-5791-974f-8bc0-3997ab1d61ea@dancol.org> (raw)
In-Reply-To: <20200720160059.GO2786714@ZenIV.linux.org.uk>
On 7/20/20 9:00 AM, Al Viro wrote:
> 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().
Yep. I don't recall how the O_CLOEXEC got in there: that's indeed wrong,
and probably the result of patch-editing butchery. As for the exit
cleanup: yes, that's a bug. I was trying to keep the exit paths
together. We could fix it forward (which seems simple enough) or re-submit.
prev parent reply other threads:[~2020-07-21 0:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 2:24 KASAN: use-after-free Read in userfaultfd_release (2) 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
2020-07-20 23:46 ` Daniel Colascione [this message]
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