linux-kernel - Re: [PATCH 1/3] Fix COW D-cache aliasing on fork

lists.openwall.net		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:	Fri, 20 Oct 2006 08:49:35 -0700 (PDT)
From:	Linus Torvalds <torvalds@...l.org>
To:	Nick Piggin <nickpiggin@...oo.com.au>
cc:	David Miller <davem@...emloft.net>, ralf@...ux-mips.org,
	akpm@...l.org, linux-kernel@...r.kernel.org, anemo@....ocn.ne.jp
Subject: Re: [PATCH 1/3] Fix COW D-cache aliasing on fork



On Sat, 21 Oct 2006, Nick Piggin wrote:
> 
> So moving the flush_cache_mm below the copy_page_range, to just
> before the flush_tlb_mm, would work then? This would make the
> race much smaller than with this patchset.
> 
> But doesn't that still leave a race?
> 
> What if another thread writes to cache after we have flushed it
> but before flushing the TLBs? Although we've marked the the ptes
> readonly, the CPU won't trap if the TLB is valid? There must be
> some special way for the arch to handle this, but I can't see it.

Why not do the cache flush _after_ the TLB flush? There's still a mapping, 
and never mind that it's read-only: the _mapping_ still exists, and I 
doubt any CPU will not do the writeback (the readonly bit had better 
affect the _frontend_ of the memory pipeline, but affectign the back end 
would be insane and very hard, since you can't raise a fault any more).

Hmm?

		Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/