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authorRussell King <rmk+kernel@armlinux.org.uk>2018-10-01 22:13:14 -0400
committerDavid A. Long <dave.long@linaro.org>2018-10-30 23:23:46 -0400
commit32310da36c3e738a738b23df491128290e69b8ce (patch)
treef94b41ef5894b3852452504f2216748c68eedc5a
parentf79b41c803919dcb44a18c4e29ab551b1f8d2d00 (diff)
downloadlinux-linaro-stable-32310da36c3e738a738b23df491128290e69b8ce.tar.gz
ARM: signal: copy registers using __copy_from_user()
Commit c32cd419d6650e42b9cdebb83c672ec945e6bd7e upstream. __get_user_error() is used as a fast accessor to make copying structure members in the signal handling path 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. It becomes much more efficient to use __copy_from_user() instead, so let's use this for the ARM integer registers. Acked-by: Mark Rutland <mark.rutland@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/kernel/signal.c38
1 files changed, 21 insertions, 17 deletions
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 7b8f2141427b..a592bc0287f8 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -141,6 +141,7 @@ struct rt_sigframe {
static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
{
+ struct sigcontext context;
struct aux_sigframe __user *aux;
sigset_t set;
int err;
@@ -149,23 +150,26 @@ static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
if (err == 0)
set_current_blocked(&set);
- __get_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
- __get_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
- __get_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
- __get_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
- __get_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
- __get_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
- __get_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
- __get_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
- __get_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
- __get_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
- __get_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
- __get_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
- __get_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
- __get_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
- __get_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
- __get_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
- __get_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);
+ err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
+ if (err == 0) {
+ regs->ARM_r0 = context.arm_r0;
+ regs->ARM_r1 = context.arm_r1;
+ regs->ARM_r2 = context.arm_r2;
+ regs->ARM_r3 = context.arm_r3;
+ regs->ARM_r4 = context.arm_r4;
+ regs->ARM_r5 = context.arm_r5;
+ regs->ARM_r6 = context.arm_r6;
+ regs->ARM_r7 = context.arm_r7;
+ regs->ARM_r8 = context.arm_r8;
+ regs->ARM_r9 = context.arm_r9;
+ regs->ARM_r10 = context.arm_r10;
+ regs->ARM_fp = context.arm_fp;
+ regs->ARM_ip = context.arm_ip;
+ regs->ARM_sp = context.arm_sp;
+ regs->ARM_lr = context.arm_lr;
+ regs->ARM_pc = context.arm_pc;
+ regs->ARM_cpsr = context.arm_cpsr;
+ }
err |= !valid_user_regs(regs);