linux-kernel - Re: [syzbot] KASAN: use-after-free Read in post_one

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Message-ID: <18261e01068.4a2910f2403165.1226720997594524412@siddh.me>
Date:   Wed, 03 Aug 2022 09:34:10 +0530
From:   Siddh Raman Pant <code@...dh.me>
To:     "Eric Biggers" <ebiggers@...nel.org>
Cc:     "syzbot" <syzbot+c70d87ac1d001f29a058@...kaller.appspotmail.com>,
        "hdanton" <hdanton@...a.com>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        "syzkaller-bugs" <syzkaller-bugs@...glegroups.com>
Subject: Re: [syzbot] KASAN: use-after-free Read in post_one_notification

On Wed, 03 Aug 2022 03:57:19 +0530  Eric Biggers <ebiggers@...nel.org> wrote:
> It appears this was already fixed, so no need for any more activity on this bug:
> 
> #syz fix: watchqueue: make sure to serialize 'wqueue->defunct' properly
> 
> - Eric

It doesn't address the dangling pointer remaining in the watch_queue,
which was the root cause of this crash. The use-after-free happened
because the pipe was freed but a dangling pointer of it remained in
a watch_queue, and an attempt to dereference it was there.

Thanks,
Siddh