linux-kernel - Re: [PATCH 5.10/5.15] io_uring: avoid null-ptr-deref in io_arm_poll

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Message-ID: <20230316192259.ec46rcfw52ubqxrp@fpc>
Date:   Thu, 16 Mar 2023 22:22:59 +0300
From:   Fedor Pchelkin <pchelkin@...ras.ru>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jens Axboe <axboe@...nel.dk>, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        lvc-project@...uxtesting.org
Subject: Re: [PATCH 5.10/5.15] io_uring: avoid null-ptr-deref in
 io_arm_poll_handler

On Thu, Mar 16, 2023 at 08:04:24PM +0100, Greg Kroah-Hartman wrote:
> 
> How can you trigger a GFP_ATOMIC memory failure?  If you do, worse
> things are about to happen to your system, right?
> 
> thanks,
> 
> greg k-h

Well, Syzkaller triggers them with fail slab, and that is more for
debugging purposes to detect improper handling of error paths.

I agree that if GFP_ATOMIC memory allocation fails then the system is in
more trouble. Do you mean this is the point not to backport it? Now I'm
actually not quite sure about this... It's not clear to me whether such
things should be backported: on one hand, it is a bug which can actually
occur (yes, in very bad situation), on the other - the whole system is not
good anyway.