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authorJulien Thierry <julien.thierry@arm.com>2019-01-09 12:55:11 -0500
committerDavid A. Long <dave.long@linaro.org>2019-02-13 12:14:33 -0500
commit8dc415cf40207a5791ec37876d416404528dd497 (patch)
treee929a85debf3a3a776d8568e46ad84a9ae219f17
parent11cda757aba11503893d7b02fc5ebdd271f04055 (diff)
downloadlinux-linaro-stable-8dc415cf40207a5791ec37876d416404528dd497.tar.gz
ARM: 8794/1: uaccess: Prevent speculative use of the current addr_limit
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>
-rw-r--r--arch/arm/include/asm/uaccess.h8
1 files changed, 8 insertions, 0 deletions
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);
}