[PATCH 7/7] arm64: uprobes - ARM32 instruction probing

On 01/24/2018 05:13 PM, Oleg Nesterov wrote:

On 01/24, Maciej Slodczyk wrote:

quoted

Detect what kind of instruction is being probed and depending on the result:
- if an A64 instruction handle it the old way, using existing A64 instructions
probing code,
- if an A32 instruction decode it and handle using the new code, moved from
32 bit arm kernel tree.

how this connects to the change in prepare_uretprobe(),

quoted

--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c

@@ -1566,6 +1566,9 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
  	unsigned long orig_ret_vaddr, trampoline_vaddr;
  	bool chained;

+	if (!current->mm)
+		return;
+

?

and how it is possible to hit ->mm == NULL here?

That's obviously something that shouldn't have been left here. NULL was 
there because of other bug that's been fixed. I put it for testing only 
and for some reason forgot to remove. Thanks for pointing that out!

Regards,
Maciej