linux-kernel - Re: [regression] Bug 216932 - io_uring with libvirt cause kernel NULL pointer dereference since 6.1.5

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Message-ID: <Y9zRPHyAmxhJoork@kroah.com>
Date:   Fri, 3 Feb 2023 10:17:48 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Linux regressions mailing list <regressions@...ts.linux.dev>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        io-uring@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        "Sergey V." <truesmb@...il.com>
Subject: Re: [regression] Bug 216932 - io_uring with libvirt cause kernel
 NULL pointer dereference since 6.1.5

On Mon, Jan 16, 2023 at 08:50:20AM -0700, Jens Axboe wrote:
> On 1/16/23 8:44 AM, Jens Axboe wrote:
> > On 1/16/23 7:49 AM, Greg Kroah-Hartman wrote:
> >> On Mon, Jan 16, 2023 at 07:13:40AM -0700, Jens Axboe wrote:
> >>> On 1/16/23 6:42 AM, Jens Axboe wrote:
> >>>> On 1/16/23 6:17?AM, Linux kernel regression tracking (Thorsten Leemhuis) wrote:
> >>>>> Hi, this is your Linux kernel regression tracker.
> >>>>>
> >>>>> I noticed a regression report in bugzilla.kernel.org. As many (most?)
> >>>>> kernel developer don't keep an eye on it, I decided to forward it by
> >>>>> mail. Quoting from https://bugzilla.kernel.org/show_bug.cgi?id=216932 :
> >>>>
> >>>> Looks like:
> >>>>
> >>>> commit 6d47e0f6a535701134d950db65eb8fe1edf0b575
> >>>> Author: Jens Axboe <axboe@...nel.dk>
> >>>> Date:   Wed Jan 4 08:52:06 2023 -0700
> >>>>
> >>>>     block: don't allow splitting of a REQ_NOWAIT bio
> >>>>
> >>>> got picked up by stable, but not the required prep patch:
> >>>>
> >>>>
> >>>> commit 613b14884b8595e20b9fac4126bf627313827fbe
> >>>> Author: Jens Axboe <axboe@...nel.dk>
> >>>> Date:   Wed Jan 4 08:51:19 2023 -0700
> >>>>
> >>>>     block: handle bio_split_to_limits() NULL return
> >>>>
> >>>> Greg/team, can you pick the latter too? It'll pick cleanly for
> >>>> 6.1-stable, not sure how far back the other patch has gone yet.
> >>>
> >>> Looked back, and 5.15 has it too, but the cherry-pick won't work
> >>> on that kernel.
> >>>
> >>> Here's one for 5.15-stable that I verified crashes before this one,
> >>> and works with it. Haven't done an allmodconfig yet...
> >>
> >> All now queued up, thanks!
> > 
> > Thanks Greg! This one was my fault, as it was a set of 2 patches and
> > I only marked 2/2 for stable. But how is that best handled? 1/2 could've
> > been marked stable as well, but I don't think that would have prevented
> > 2/2 applying fine and 1/2 failing and hence not getting queued up until
> > I would've done a backport.
> > 
> > What's the recommended way to describe the dependency that you only
> > want 2/2 applied when 1/2 is in as well?
> 
> What I'm asking is if we have something like Depends-on or similar
> that would explain this dependency. Then patch 2/2 could have:
> 
> Depends-on: 613b14884b85 ("block: handle bio_split_to_limits() NULL return")
> 
> and then it'd be clear that either both get added, or none of them.

As per the documentation, you can put this on the cc: stable line in the
changelog text like:
  cc: stable <stable@...r.kernel.org> # 613b14884b85

thanks,

greg k-h