lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Tue, 24 Jul 2007 10:22:07 +0200
From:	Jens Axboe <>
To:	Andrew Morton <>
Cc:	Alexey Dobriyan <>,
	Linus Torvalds <>,,,,
Subject: Re: 2.6.23-rc1: BUG_ON in kmap_atomic_prot()

On Tue, Jul 24 2007, Jens Axboe wrote:
> On Mon, Jul 23 2007, Andrew Morton wrote:
> > I worked out that the crash I saw was in
> > 
> >         BUG_ON(!pte_none(*(kmap_pte-idx)));
> > 
> > in the read of kmap_pte[idx].  Which would be weird as the caller is using 
> > a literal KM_USER0.
> > 
> > So maybe I goofed, and that BUG_ON is triggering (it scrolled off, and I am
> > unable to reproduce it now).
> > 
> > If that BUG_ON _is_ triggering then it might indicate that someone is doing
> > a __GFP_HIGHMEM|__GFP_ZERO allocation while holding KM_USER0.
> Or doing double kunmaps, or doing a kunmap_atomic() on the page, not the
> address. I've seen both of those end up triggering that BUG_ON() in a
> later kmap.
> Looking over the 2.6.22..2.6.23-rc1 diff, I found one such error in
> ocfs2 at least. But you are probably not using that, so I'll keep
> looking...

What about the new async crypto stuff? I've been looking, but is it
guarenteed that async_memcpy() runs in process context with interrupts
enabled always? If not, there's a km type bug there.

In general, I think the highmem stuff could do with more safety checks:

- People ALWAYS get the atomic unmaps wrong, passing in the page instead
  of the address. I've seen tons of these. And since kunmap_atomic()
  takes a void pointer, nobody notices until it goes boom.
- People easily get the km type wrong - they use KM_USERx in interrupt
  context, or one of the irq variants without disabling interrupts.

If we could just catch these two types of bugs, we've got a lot of these
problems covered.

Jens Axboe

To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists