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

On Thu, 7 Jan 2021 11:47:02 -0800
Linus Torvalds [off-list ref] wrote:

On Wed, Jan 6, 2021 at 8:45 PM Willem de Bruijn [off-list ref] wrote:

quoted

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/ (local)
  Reported-by: Steven Rostedt (VMware) [off-list ref]

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

  Tested-by: Steven Rostedt (VMware) [off-list ref]

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

Thanks!

-- Steve