linux-kernel - Re: [BUG] from x86: Support kmap

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Date:   Thu, 7 Jan 2021 15:52:56 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Willem de Bruijn <willemb@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: [BUG] from x86: Support kmap_local() forced debugging

On Thu, 7 Jan 2021 11:47:02 -0800
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Wed, Jan 6, 2021 at 8:45 PM Willem de Bruijn <willemb@...gle.com> wrote:
> >
> > But there are three other kmap_atomic callers under net/ that do not
> > loop at all, so assume non-compound pages. In esp_output_head,
> > esp6_output_head and skb_seq_read. The first two directly use
> > skb_page_frag_refill, which can allocate compound (but not
> > __GFP_HIGHMEM) pages, and the third can be inserted with
> > netfilter xt_string in the path of tcp transmit skbs, which can also
> > have compound pages. I think that these could similarly access
> > data beyond the end of the kmap_atomic mapped page. I'll take
> > a closer look.  
> 
> Thanks.
> 
> Note that I have flushed my random one-liner patch from my system, and
> expect to get a proper fix through the normal networking pulls.
> 
> And _if_ the networking people feel that my one-liner was the proper
> fix, you can use it and add my sign-off if you want to, but it really
> was more of a "this is the quick ugly fix for testing" rather than
> anything else.
> 

Please add:

  Link: https://lore.kernel.org/linux-mm/20210106180132.41dc249d@gandalf.local.home/
  Reported-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

And if you take Linus's patch, please add my:

  Tested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

and if you come up with another patch, please send it to me for testing.

Thanks!

-- Steve