[PATCH ARM32 v4.4 V2 32/47] ARM: 8794/1: uaccess: Prevent speculative use of the current addr_limit
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: 2019-08-01 08:20:59
Also in:
stable
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
From: Julien Thierry <redacted>
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 <redacted>
Signed-off-by: Russell King <redacted>
Signed-off-by: Viresh Kumar <viresh.kumar@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 ecd159b45f12..a782201a2629 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); }
--
2.21.0.rc0.269.g1a574e7a288b
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