From 71b5200f5f0c1e9966dd7d238526e85f4fbf8089 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Thu, 29 Sep 2016 18:18:23 -0400 Subject: [PATCH] arm64: kprobes: Fix overflow when saving stack commit ab4c1325d4bf111a590a1f773e3d93bde7f40201 upstream. The MIN_STACK_SIZE macro tries evaluate how much stack space needs to be saved in the jprobes_stack array, sized at 128 bytes. When using the IRQ stack, said macro can happily return up to IRQ_STACK_SIZE, which is 16kB. Mayhem follows. This patch fixes things by getting rid of the crazy macro and limiting the copy to be at most the size of the jprobes_stack array, no matter which stack we're on. [dave.long@linaro.org: Since there is no irq_stack in this kernel version this fix is not strictly necessary, but is included for completeness.] Signed-off-by: Marc Zyngier Signed-off-by: Catalin Marinas Signed-off-by: David A. Long --- arch/arm64/kernel/probes/kprobes.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index a9b274c99519..b1189741dbb0 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -34,9 +34,6 @@ #include "decode-insn.h" -#define MIN_STACK_SIZE(addr) min((unsigned long)MAX_STACK_SIZE, \ - (unsigned long)current_thread_info() + THREAD_START_SP - (addr)) - void jprobe_return_break(void); DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; @@ -45,6 +42,15 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); static void __kprobes post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *); +static inline unsigned long min_stack_size(unsigned long addr) +{ + unsigned long size; + + size = (unsigned long)current_thread_info() + THREAD_START_SP - addr; + + return min(size, FIELD_SIZEOF(struct kprobe_ctlblk, jprobes_stack)); +} + static void __kprobes arch_prepare_ss_slot(struct kprobe *p) { /* prepare insn slot */ @@ -492,7 +498,7 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) * the argument area. */ memcpy(kcb->jprobes_stack, (void *)stack_ptr, - MIN_STACK_SIZE(stack_ptr)); + min_stack_size(stack_ptr)); instruction_pointer_set(regs, (unsigned long) jp->entry); preempt_disable(); @@ -545,7 +551,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) unpause_graph_tracing(); *regs = kcb->jprobe_saved_regs; memcpy((void *)stack_addr, kcb->jprobes_stack, - MIN_STACK_SIZE(stack_addr)); + min_stack_size(stack_addr)); preempt_enable_no_resched(); return 1; } -- 2.34.1