Re: [BUG] from x86: Support kmap_local() forced debugging

From: Steven Rostedt <rostedt@goodmis.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Willem de Bruijn <willemb@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	David Miller <davem@davemloft.net>,
	Jonathan Lemon <jonathan.lemon@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Christoph Hellwig <hch@lst.de>,
	Matthew Wilcox <willy@infradead.org>,
	Daniel Vetter <daniel@ffwll.ch>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux-MM <linux-mm@kvack.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Netdev <netdev@vger.kernel.org>
Subject: Re: [BUG] from x86: Support kmap_local() forced debugging
Date: Thu, 7 Jan 2021 15:52:56 -0500	[thread overview]
Message-ID: <20210107155256.7af2505e@gandalf.local.home> (raw)
In-Reply-To: <CAHk-=wh+KfbJ4Wrz4A+hFRRj7ZYWysz9L8s-BosC3bhV6vN-nQ@mail.gmail.com>

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

> On Wed, Jan 6, 2021 at 8:45 PM Willem de Bruijn <willemb@google.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@goodmis.org>

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

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

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

Thanks!

-- Steve