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authorWill Deacon <will.deacon@arm.com>2018-02-05 15:34:21 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2018-02-06 22:53:37 +0000
commitc2f0ad4fc089cff81cef6a13d04b399980ecbfcc (patch)
tree758d9a7e84a17ed49848d88cc687af1c29624ac7 /arch/arm64
parent6314d90e64936c584f300a52ef173603fb2461b5 (diff)
arm64: uaccess: Prevent speculative use of the current addr_limit
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. Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/include/asm/uaccess.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index e49fe723d72d..2057deed7697 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -42,6 +42,13 @@ 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();
+
/* On user-mode return, check fs is correct */
set_thread_flag(TIF_FSCHECK);