arm64: kprobes: Add KASAN instrumentation around stack accesses

This patch disables KASAN around the memcpy from/to the kernel or IRQ
stacks to avoid warnings like below:

BUG: KASAN: stack-out-of-bounds in setjmp_pre_handler+0xe4/0x170 at addr ffff800935cbbbc0
Read of size 128 by task swapper/0/1
page:ffff7e0024d72ec0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x1000000000000000()
page dumped because: kasan: bad access detected
CPU: 4 PID: 1 Comm: swapper/0 Not tainted 4.7.0-rc4+ #1
Hardware name: ARM Juno development board (r0) (DT)
Call trace:
[<ffff20000808ad88>] dump_backtrace+0x0/0x280
[<ffff20000808b01c>] show_stack+0x14/0x20
[<ffff200008563a64>] dump_stack+0xa4/0xc8
[<ffff20000824a1fc>] kasan_report_error+0x4fc/0x528
[<ffff20000824a5e8>] kasan_report+0x40/0x48
[<ffff20000824948c>] check_memory_region+0x144/0x1a0
[<ffff200008249814>] memcpy+0x34/0x68
[<ffff200008c3ee2c>] setjmp_pre_handler+0xe4/0x170
[<ffff200008c3ec5c>] kprobe_breakpoint_handler+0xec/0x1d8
[<ffff2000080853a4>] brk_handler+0x5c/0xa0
[<ffff2000080813f0>] do_debug_exception+0xa0/0x138

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/probes/kprobes.c

@@ -16,6 +16,7 @@
  * General Public License for more details.
  *
  */
+#include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/kprobes.h>
 #include <linux/module.h>
@@ -498,8 +499,10 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 	 * we also save and restore enough stack bytes to cover
 	 * the argument area.
 	 */
+	kasan_disable_current();
 	memcpy(kcb->jprobes_stack, (void *)stack_ptr,
 	       min_stack_size(stack_ptr));
+	kasan_enable_current();
 
 	instruction_pointer_set(regs, (unsigned long) jp->entry);
 	preempt_disable();
@@ -551,8 +554,10 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 	}
 	unpause_graph_tracing();
 	*regs = kcb->jprobe_saved_regs;
+	kasan_disable_current();
 	memcpy((void *)stack_addr, kcb->jprobes_stack,
 	       min_stack_size(stack_addr));
+	kasan_enable_current();
 	preempt_enable_no_resched();
 	return 1;
 }