From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.101.70]:59360 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752428AbeDLLMQ (ORCPT ); Thu, 12 Apr 2018 07:12:16 -0400 From: Mark Rutland To: stable@vger.kernel.org Cc: mark.brown@linaro.org, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, will.deacon@arm.com, catalin.marinas@arm.com, ghackmann@google.com, shankerd@codeaurora.org Subject: [PATCH v4.9.y 07/42] arm64: uaccess: Prevent speculative use of the current addr_limit Date: Thu, 12 Apr 2018 12:11:03 +0100 Message-Id: <20180412111138.40990-8-mark.rutland@arm.com> In-Reply-To: <20180412111138.40990-1-mark.rutland@arm.com> References: <20180412111138.40990-1-mark.rutland@arm.com> Sender: stable-owner@vger.kernel.org List-ID: From: Will Deacon commit c2f0ad4fc089cff81cef6a13d04b399980ecbfcc upstream. A mispredicted conditional call to set_fs could result in the wrong addr_limit being forwarded under speculation to a subsequent access_ok check, potentially forming part of a spectre-v1 attack using uaccess routines. This patch prevents this forwarding from taking place, but putting heavy barriers in set_fs after writing the addr_limit. Reviewed-by: Mark Rutland Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Mark Rutland [v4.9 backport] --- arch/arm64/include/asm/uaccess.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index a9db051b967f..900397e73fa6 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -68,6 +68,13 @@ static inline void set_fs(mm_segment_t fs) current_thread_info()->addr_limit = fs; /* + * Prevent a mispredicted conditional call to set_fs from forwarding + * the wrong address limit to access_ok under speculation. + */ + dsb(nsh); + isb(); + + /* * Enable/disable UAO so that copy_to_user() etc can access * kernel memory with the unprivileged instructions. */ -- 2.11.0