From 18b7a6bef62de1d598fbff23b52114b7775ecf00 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Sun, 14 Apr 2019 18:00:07 +0200 Subject: [PATCH] x86/irq/64: Remap the IRQ stack with guard pages The IRQ stack lives in percpu space, so an IRQ handler that overflows it will overwrite other data structures. Use vmap() to remap the IRQ stack so that it will have the usual guard pages that vmap()/vmalloc() allocations have. With this, the kernel will panic immediately on an IRQ stack overflow. [ tglx: Move the map code to a proper place and invoke it only when a CPU is about to be brought online. No point in installing the map at early boot for all possible CPUs. Fail the CPU bringup if the vmap() fails as done for all other preparatory stages in CPU hotplug. ] Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov Cc: "H. Peter Anvin" Cc: Andy Lutomirski Cc: Ingo Molnar Cc: Josh Poimboeuf Cc: Nicolai Stange Cc: Sean Christopherson Cc: x86-ml Link: https://lkml.kernel.org/r/20190414160146.363733568@linutronix.de --- arch/x86/kernel/irq_64.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c index c0f89d136b80..f107eb2021f6 100644 --- a/arch/x86/kernel/irq_64.c +++ b/arch/x86/kernel/irq_64.c @@ -91,6 +91,35 @@ bool handle_irq(struct irq_desc *desc, struct pt_regs *regs) return true; } +#ifdef CONFIG_VMAP_STACK +/* + * VMAP the backing store with guard pages + */ +static int map_irq_stack(unsigned int cpu) +{ + char *stack = (char *)per_cpu_ptr(&irq_stack_backing_store, cpu); + struct page *pages[IRQ_STACK_SIZE / PAGE_SIZE]; + void *va; + int i; + + for (i = 0; i < IRQ_STACK_SIZE / PAGE_SIZE; i++) { + phys_addr_t pa = per_cpu_ptr_to_phys(stack + (i << PAGE_SHIFT)); + + pages[i] = pfn_to_page(pa >> PAGE_SHIFT); + } + + va = vmap(pages, IRQ_STACK_SIZE / PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL); + if (!va) + return -ENOMEM; + + per_cpu(hardirq_stack_ptr, cpu) = va + IRQ_STACK_SIZE; + return 0; +} +#else +/* + * If VMAP stacks are disabled due to KASAN, just use the per cpu + * backing store without guard pages. + */ static int map_irq_stack(unsigned int cpu) { void *va = per_cpu_ptr(&irq_stack_backing_store, cpu); @@ -98,6 +127,7 @@ static int map_irq_stack(unsigned int cpu) per_cpu(hardirq_stack_ptr, cpu) = va + IRQ_STACK_SIZE; return 0; } +#endif int irq_init_percpu_irqstack(unsigned int cpu) { -- 2.30.2