From: Matthew Wilcox <willy@infradead.org>
To: David Laight <David.Laight@aculab.com>
Cc: 'Sagi Grimberg' <sagi@grimberg.me>,
kernel test robot <oliver.sang@intel.com>,
"oe-lkp@lists.linux.dev" <oe-lkp@lists.linux.dev>,
"lkp@intel.com" <lkp@intel.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>
Subject: Re: [PATCH] net: micro-optimize skb_datagram_iter
Date: Sun, 16 Jun 2024 22:53:20 +0100 [thread overview]
Message-ID: <Zm9e0OpCaucP4836@casper.infradead.org> (raw)
In-Reply-To: <e2bce6704b20491e8eb2edd822ae6404@AcuMS.aculab.com>
On Sun, Jun 16, 2024 at 09:51:05PM +0000, David Laight wrote:
> From: Sagi Grimberg
> > Sent: 16 June 2024 10:24
> ...
> > > [ 13.498663][ T189] EIP: usercopy_abort (mm/usercopy.c:102 (discriminator 12))
> > > [ 13.499424][ T194] usercopy: Kernel memory exposure attempt detected from kmap (offset 0, size
> > 8192)!
> >
> > Hmm, not sure I understand exactly why changing kmap() to
> > kmap_local_page() expose this,
> > but it looks like mm/usercopy does not like size=8192 when copying for
> > the skb frag.
>
> Can't a usercopy fault and have to read the page from swap?
> So the process can sleep and then be rescheduled on a different cpu?
> So you can't use kmap_local_page() here at all.
I don't think you understand how kmap_local_page() works.
next prev parent reply other threads:[~2024-06-16 21:53 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-13 11:35 [PATCH] net: micro-optimize skb_datagram_iter Sagi Grimberg
2024-06-15 2:40 ` patchwork-bot+netdevbpf
2024-06-16 8:06 ` kernel test robot
2024-06-16 9:24 ` Sagi Grimberg
2024-06-16 21:51 ` David Laight
2024-06-16 21:53 ` Matthew Wilcox [this message]
2024-06-17 10:18 ` David Laight
2024-06-16 21:56 ` Matthew Wilcox
2024-06-17 6:29 ` Sagi Grimberg
2024-06-17 16:58 ` Jakub Kicinski
2024-06-18 6:37 ` Sagi Grimberg
2024-06-19 12:46 ` David Howells
2024-06-19 13:54 ` Sagi Grimberg
2024-06-19 14:51 ` Eric Dumazet
2024-06-19 14:56 ` Eric Dumazet
2024-06-19 15:25 ` Sagi Grimberg
2024-06-21 7:54 ` David Howells
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