[4.9,V2,19/24] ARM: signal: copy registers using __copy_from_user()

Message ID 20181107164402.9380-20-dave.long@linaro.org
State New
Headers show
Series
  • V4.9 backport of 32-bit arm spectre patches
Related show

Commit Message

David Long Nov. 7, 2018, 4:43 p.m.
From: Russell King <rmk+kernel@armlinux.org.uk>


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>

---
 arch/arm/kernel/signal.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

-- 
2.17.1

Patch

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);