From 8c8484a1c18e3231648f5ba7cc5ffb7fd70b3ca4 Mon Sep 17 00:00:00 2001 From: Russell King Date: Mon, 9 Jul 2018 10:20:06 +0100 Subject: [PATCH] ARM: oabi-compat: copy semops using __copy_from_user() __get_user_error() is used as a fast accessor to make copying structure members as efficient as possible. However, with software PAN and the recent Spectre variant 1, the efficiency is reduced as these are no longer fast accessors. In the case of software PAN, it has to switch the domain register around each access, and with Spectre variant 1, it would have to repeat the access_ok() check for each access. Rather than using __get_user_error() to copy each semops element member, copy each semops element in full using __copy_from_user(). Acked-by: Mark Rutland Signed-off-by: Russell King --- arch/arm/kernel/sys_oabi-compat.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/arm/kernel/sys_oabi-compat.c b/arch/arm/kernel/sys_oabi-compat.c index b9786f491873..4abe4909417f 100644 --- a/arch/arm/kernel/sys_oabi-compat.c +++ b/arch/arm/kernel/sys_oabi-compat.c @@ -329,9 +329,11 @@ asmlinkage long sys_oabi_semtimedop(int semid, return -ENOMEM; err = 0; for (i = 0; i < nsops; i++) { - __get_user_error(sops[i].sem_num, &tsops->sem_num, err); - __get_user_error(sops[i].sem_op, &tsops->sem_op, err); - __get_user_error(sops[i].sem_flg, &tsops->sem_flg, err); + struct oabi_sembuf osb; + err |= __copy_from_user(&osb, tsops, sizeof(osb)); + sops[i].sem_num = osb.sem_num; + sops[i].sem_op = osb.sem_op; + sops[i].sem_flg = osb.sem_flg; tsops++; } if (timeout) {