linux-kernel - Re: [PATCH v2] fs/pipe: Deinitialize the watch

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Message-ID: <YvJ/XzuyWbZT2dlO@google.com>
Date:   Tue, 9 Aug 2022 16:38:07 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Haimin Zhang <tcs.kernel@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Haimin Zhang <tcs_kernel@...cent.com>,
        TCS Robot <tcs_robot@...cent.com>, Lee Jones <lee@...nel.org>
Subject: Re: [PATCH v2] fs/pipe: Deinitialize the watch_queue when pipe is
 freed

On Tue, 02 Aug 2022, Eric Biggers wrote:

> On Tue, Jul 19, 2022 at 03:04:41PM +0100, Lee Jones wrote:
> > On Wed, 06 Jul 2022, Lee Jones wrote:
> > 
> > > On Mon, 09 May 2022, Eric Biggers wrote:
> > > 
> > > > On Mon, May 09, 2022 at 09:17:26PM +0800, Haimin Zhang wrote:
> > > > > From: Haimin Zhang <tcs_kernel@...cent.com>
> > > > > 
> > > > > Add a new function call to deinitialize the watch_queue of a freed pipe.
> > > > > When a pipe node is freed, it doesn't make pipe->watch_queue->pipe null.
> > > > > Later when function post_one_notification is called, it will use this
> > > > > field, but it has been freed and watch_queue->pipe is a dangling pointer.
> > > > > It makes a uaf issue.
> > > > > Check wqueu->defunct before pipe check since pipe becomes invalid once all
> > > > > watch queues were cleared.
> > > > > 
> > > > > Reported-by: TCS Robot <tcs_robot@...cent.com>
> > > > > Signed-off-by: Haimin Zhang <tcs_kernel@...cent.com>
> > > > 
> > > > Is this fixing something?  If so it should have a "Fixes" tag.
> > > 
> > > It sure is.
> > > 
> > > Haimin, are you planning a v3?
> > 
> > This patch is set to fix a pretty public / important bug.
> > 
> > Has there been any more activity that I may have missed?
> > 
> > Perhaps it's been superseded?
> 
> I think this was already fixed (correctly, unlike the above patch which is very
> broken) by the following commit:
> 
> 	commit 353f7988dd8413c47718f7ca79c030b6fb62cfe5
> 	Author: Linus Torvalds <torvalds@...ux-foundation.org>
> 	Date:   Tue Jul 19 11:09:01 2022 -0700
> 
> 	    watchqueue: make sure to serialize 'wqueue->defunct' properly

Thanks Eric, I'll back-port this one instead.

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