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Subject: Re: [PATCH] x86 page fault handler not interrupt safe
To: torvalds@transmeta.com (Linus Torvalds)
Date: Mon, 7 May 2001 22:37:10 +0100 (BST)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), bgerst@didntduck.org (Brian Gerst),
        linux-kernel@vger.kernel.org
In-Reply-To: <Pine.LNX.4.21.0105071003330.12733-100000@penguin.transmeta.com> from "Linus Torvalds" at May 07, 2001 10:12:58 AM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> If anybody has such a beast, please try this kernel patch _and_ running
> the F0 0F bug-producing program (search for it on the 'net - it must be

One apparent problem with this implementation

> +	 *
> +	 * This verifies that the fault happens in kernel space
> +	 * (error_code & 4) == 0, and that the fault was not a
> +	 * protection error (error_code & 1) == 0.
>  	 */
> -	if (address >= TASK_SIZE)
> +	if (address >= TASK_SIZE && !(error_code & 5))
>  		goto vmalloc_fault;

address might be from the following vmalloc fault. The error code would
indicate user space, so we would do a bogus user space fix up for vmalloc
space, fault and die.