From: Will Deacon Date: Mon, 5 Feb 2018 15:34:21 +0000 (+0000) Subject: arm64: uaccess: Prevent speculative use of the current addr_limit X-Git-Tag: v4.16-rc1~34^2~22 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=c2f0ad4fc089cff8;p=linux.git 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 Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas --- 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);