From: Will Deacon will.deacon@arm.com
commit 30d88c0e3ace625a92eead9ca0ad94093a8f59fe upstream.
It is possible to take an IRQ from EL0 following a branch to a kernel address in such a way that the IRQ is prioritised over the instruction abort. Whilst an attacker would need to get the stars to align here, it might be sufficient with enough calibration so perform BP hardening in the rare case that we see a kernel address in the ELR when handling an IRQ from EL0.
Reported-by: Dan Hettena dhettena@nvidia.com Reviewed-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- arch/arm64/kernel/entry.S | 5 +++++ arch/arm64/mm/fault.c | 6 ++++++ 2 files changed, 11 insertions(+)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 42a141f01f3b..1548be9732ce 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -582,6 +582,11 @@ ENDPROC(el0_sync) #endif
ct_user_exit +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR + tbz x22, #55, 1f + bl do_el0_irq_bp_hardening +1: +#endif irq_handler
#ifdef CONFIG_TRACE_IRQFLAGS diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 082f385b6592..9ff48d083c4c 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -535,6 +535,12 @@ asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr, arm64_notify_die("", regs, &info, esr); }
+asmlinkage void __exception do_el0_irq_bp_hardening(void) +{ + /* PC has already been checked in entry.S */ + arm64_apply_bp_hardening(); +} + asmlinkage void __exception do_el0_ia_bp_hardening(unsigned long addr, unsigned int esr, struct pt_regs *regs)