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[72.71.243.63]) by smtp.googlemail.com with ESMTPSA id k66sm1498919qkc.25.2019.02.14.06.49.38 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Feb 2019 06:49:39 -0800 (PST) From: David Long To: stable@vger.kernel.org, Russell King - ARM Linux , Florian Fainelli , Julien Thierry , Tony Lindgren , Marc Zyngier , Greg KH , Mark Rutland Cc: Will Deacon , Mark Brown , linux-kernel@vger.kernel.org Subject: [PATCH 4.9 05/16] ARM: 8794/1: uaccess: Prevent speculative use of the current addr_limit Date: Thu, 14 Feb 2019 09:49:19 -0500 Message-Id: <20190214144930.27539-6-dave.long@linaro.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190214144930.27539-1-dave.long@linaro.org> References: <20190214144930.27539-1-dave.long@linaro.org> From: Julien Thierry Commit 621afc677465db231662ed126ae1f355bf8eac47 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. Porting commit c2f0ad4fc089cff8 ("arm64: uaccess: Prevent speculative use of the current addr_limit"). Signed-off-by: Julien Thierry Signed-off-by: Russell King Signed-off-by: David A. Long --- arch/arm/include/asm/uaccess.h | 8 ++++++++ 1 file changed, 8 insertions(+) -- 2.17.1 diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index 7b17460127fd..9ae888775743 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -99,6 +99,14 @@ extern int __put_user_bad(void); 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(); + modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER); }