From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f193.google.com ([209.85.222.193]:36729 "EHLO mail-qk1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726703AbeJOXSb (ORCPT ); Mon, 15 Oct 2018 19:18:31 -0400 Received: by mail-qk1-f193.google.com with SMTP id a85-v6so12075843qkg.3 for ; Mon, 15 Oct 2018 08:32:46 -0700 (PDT) From: David Long To: , Russell King - ARM Linux , Florian Fainelli , Tony Lindgren , Marc Zyngier , Mark Rutland Cc: Greg KH , Mark Brown Subject: [PATCH 4.14 23/24] ARM: spectre-v1: use get_user() for __get_user() Date: Mon, 15 Oct 2018 11:32:17 -0400 Message-Id: <1539617538-22328-24-git-send-email-dave.long@linaro.org> In-Reply-To: <1539617538-22328-1-git-send-email-dave.long@linaro.org> References: <1539617538-22328-1-git-send-email-dave.long@linaro.org> Sender: stable-owner@vger.kernel.org List-ID: From: Russell King Commit b1cd0a14806321721aae45f5446ed83a3647c914 upstream. Fixing __get_user() for spectre variant 1 is not sane: we would have to add address space bounds checking in order to validate that the location should be accessed, and then zero the address if found to be invalid. Since __get_user() is supposed to avoid the bounds check, and this is exactly what get_user() does, there's no point having two different implementations that are doing the same thing. So, when the Spectre workarounds are required, make __get_user() an alias of get_user(). Acked-by: Mark Rutland Signed-off-by: Russell King Signed-off-by: David A. Long --- arch/arm/include/asm/uaccess.h | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index 29fa6f3..4140be4 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -250,6 +250,16 @@ static inline void set_fs(mm_segment_t fs) #define user_addr_max() \ (uaccess_kernel() ? ~0UL : get_fs()) +#ifdef CONFIG_CPU_SPECTRE +/* + * When mitigating Spectre variant 1, it is not worth fixing the non- + * verifying accessors, because we need to add verification of the + * address space there. Force these to use the standard get_user() + * version instead. + */ +#define __get_user(x, ptr) get_user(x, ptr) +#else + /* * The "__xxx" versions of the user access functions do not verify the * address space - it must have been done previously with a separate @@ -266,12 +276,6 @@ static inline void set_fs(mm_segment_t fs) __gu_err; \ }) -#define __get_user_error(x, ptr, err) \ -({ \ - __get_user_err((x), (ptr), err); \ - (void) 0; \ -}) - #define __get_user_err(x, ptr, err) \ do { \ unsigned long __gu_addr = (unsigned long)(ptr); \ @@ -331,6 +335,7 @@ do { \ #define __get_user_asm_word(x, addr, err) \ __get_user_asm(x, addr, err, ldr) +#endif #define __put_user_switch(x, ptr, __err, __fn) \ -- 2.5.0