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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm/kernel/signal.c | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-)
--- 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_re 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);