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Message-ID: <87k5hpgqwa.fsf@basil.nowhere.org> Date: Tue, 20 May 2008 13:24:05 +0200 From: Andi Kleen <andi@...stfloor.org> To: Avi Kivity <avi@...ranet.com> Cc: Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] Make LIST_POISON less deadly Avi Kivity <avi@...ranet.com> writes: > The list macros use LIST_POISON1 and LIST_POISON2 as undereferencable > pointers in order to trap erronous use of freed list_heads. Unfortunately > userspace can arrange for those pointers to actually be dereferencable, > potentially turning an oops to an expolit. > > To avoid this allow architectures (currently x86_64 only) to override > the default values for these pointers with truly-undereferncable values. > This is easy on x86_64 as the virtual address space is smaller than > the range spanned by pointer values. Hmm, thought I had sent a reply earlier, but don't see it so again. My apologies if you see it twice. The problem with your address values is that they're non canonical and will result in a #GP, not #PF and oops handler cannot display the address which will make them much less obvious. I would rather use a guaranteed to be unmapped but canonical address like in the ffffc10000000000 - ffffc1ffffffffff range so that you still get page faults. -Andi -- 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/
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