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ARM: 8794/1: uaccess: Prevent speculative use of the current addr_limit

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Commit 621afc6774 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 c2f0ad4fc0 ("arm64: uaccess: Prevent speculative use
of the current addr_limit").

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David A. Long <dave.long@linaro.org>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Julien Thierry 2019-02-13 16:32:12 -05:00 committed by Greg Kroah-Hartman
parent ba22d59418
commit 39b282ade6
1 changed files with 8 additions and 0 deletions
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8
arch/arm/include/asm/uaccess.h
View file

@ -69,6 +69,14 @@ extern int __put_user_bad(void);
static inline void set_fs(mm_segment_t fs) static inline void set_fs(mm_segment_t fs)
{ {
current_thread_info()->addr_limit = 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); modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER);
} }