linux-kernel - Withdraw: [PATCH] x86-64: fix another kernel data leak to 32-bit processes

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Date:	Tue, 20 Oct 2009 07:13:24 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<stable@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: Withdraw: [PATCH] x86-64: fix another kernel data leak to
	 32-bit processes

>Unfortunately I didn't realize that the other instances of branches to
>int_ret_from_sys_call also need fixing when preparing the previous
>similar patch. The issue fixed here was in fact introduced by an
>earlier patch of mine (295286a89107c353b9677bc604361c537fd6a1c0, i.e.
>in 2.6.28, but through stable now also present in 2.6.27), making
>kernel stack contents potentially visible through R8...R11 when an
>this or earlier syscall got interrupted prior to the handler being able
>to decrement the stack pointer (such that the space normally used by
>those registers within pt_regs would get overwritten by the interrupt
>handler stub).

That analysis wasn't right after all - there's a CLEAR_RREGS in each of
the modified paths already, so the change is unnecessary (and adding
redundant code). Please don't apply it.

>While touching the code, I also swapped the branch pairs so that the
>static branch prediction logic would consider the syscall-number-in-
>range case the taken path.

If this would seem a worthwhile change, I can re-send it as a separate,
lower priority patch...

Jan

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