Messages in this thread Patch in this message | | | From | David Long <> | Subject | [PATCH 4.19 06/17] ARM: 8794/1: uaccess: Prevent speculative use of the current addr_limit | Date | Wed, 13 Feb 2019 16:32:12 -0500 |
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From: Julien Thierry <julien.thierry@arm.com>
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 <julien.thierry@arm.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> Signed-off-by: David A. Long <dave.long@linaro.org> --- arch/arm/include/asm/uaccess.h | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index 5451e1f05a19..d65ef85fc617 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -69,6 +69,14 @@ 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); } -- 2.17.1
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