Re: [PATCH] kernel/watch_queue: Make pipe NULL while clearing watch_queue

From: Hillf Danton <hdanton@sina.com>
To: Dipanjan Das <mail.dipanjan.das@gmail.com>,
	Siddh Raman Pant <code@siddh.me>
Cc: LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org
Subject: Re: [PATCH] kernel/watch_queue: Make pipe NULL while clearing watch_queue
Date: Tue,  2 Aug 2022 05:06:55 +0800	[thread overview]
Message-ID: <20220801210655.1376-1-hdanton@sina.com> (raw)
In-Reply-To: <1825594fdb6.52eb2a02235647.5426665702277259900@siddh.me>

On Mon, 01 Aug 2022 00:16:43 +0530 Siddh Raman Pant wrote:
> On Sun, 31 Jul 2022 23:41:31 +0530  Dipanjan Das <mail.dipanjan.das@gmail.com> wrote:
> > On Wed, Jul 27, 2022 at 09:50:52PM +0530, Siddh Raman Pant wrote:
> > > Thank you for explaining it!
> > >=20
> > > I will send a v3. Should I add a Suggested-by tag mentioning you?
> >=20
> > Sorry for jumping in.
> >=20
> > We have reported the same bug in kernel v5.10.131 [https://lore.kernel.or=
> g/all/CANX2M5bHye2ZEEhEV6PUj1kYL2KdWYeJtgXw8KZRzwrNpLYz+A@mail.gmail.com]. =
> We have been suggested to join this discussion so that we can have appropri=
> ate meta-information injected in this patch=E2=80=99s commit message to mak=
> e sure that it gets backported to v5.10.y.  Therefore, we would like to be =
> in the loop so that we can offer help in the process, if needed.
> >=20
> 
> As you are suggesting for backporting, I should CC the stable list, or mail
> after it gets merged. You have reproduced it on v5.10, but the change seems=
>  to
> be introduced by c73be61cede5 ("pipe: Add general notification queue suppor=
> t"),
> which got in at v5.8. So should it be backported till v5.8 instead?
> 
> I actually looked this up on the internet / lore now for any other reports,=
>  and
> it seems this fixes a CVE (CVE-2022-1882).
> 
> The reporter of CVE seems to have linked his patch as a part of CVE report,=
>  of
> which he sent v2, but he seems to do it in a roundabout way, and also in a =
> way
> similar to what Hillf Danton had replied to my v2 patch, wherein he missed
> 353f7988dd84 ("watchqueue: make sure to serialize 'wqueue->defunct' properl=
> y"),
> so I guess I can propose my patch as a fix for the CVE.

What is not clear is what you are fixing, with CVE-2022-1882 put aside,
given the mainline tree survived the syzbot test [1] irrespective of
other fixing efforts [2, 3].

Hillf

[1] https://lore.kernel.org/lkml/000000000000c7a83905e52bd127@google.com/

	syzbot has tested the proposed patch and the reproducer did not trigger any issue:

	Reported-and-tested-by: syzbot+c70d87ac1d001f29a058@syzkaller.appspotmail.com

	Tested on:

	commit:         3d7cb6b0 Linux 5.19
	git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
	console output: https://syzkaller.appspot.com/x/log.txt?x=14066d7a080000
	kernel config:  https://syzkaller.appspot.com/x/.config?x=70dd99d568a89e0
	dashboard link: https://syzkaller.appspot.com/bug?extid=c70d87ac1d001f29a058
	compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

	Note: no patches were applied.
	Note: testing is done by a robot and is best-effort only.

[2] https://lore.kernel.org/lkml/0000000000000dac0205e479ea39@google.com/
[3] https://lore.kernel.org/lkml/00000000000014c7ad05e4d535fc@google.com/

> 
> Note: I have already sent the v3, so please suggest any new improvements et=
> c.
> (except replying to the conversation here) to the v3, which can be found he=
> re:
> https://lore.kernel.org/linux-kernel/20220728155121.12145-1-code@siddh.me/
> 
> Also, you may want to break text into multiples lines instead of one huge l=
> ine.
> 
> Thanks,
> Siddh