Re: [PATCH] powerpc: Don't print kernel instructions in show_user_instructions()

Christophe LEROY [off-list ref] writes:

Le 05/10/2018 à 15:21, Michael Ellerman a écrit :

quoted

Recently we implemented show_user_instructions() which dumps the code

...

quoted

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 913c5725cdb2..bb6ac471a784 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c

@@ -1306,6 +1306,16 @@ void show_user_instructions(struct pt_regs *regs)
  
  	pc = regs->nip - (instructions_to_print * 3 / 4 * sizeof(int));
  
+	/*
+	 * Make sure the NIP points at userspace, not kernel text/data or
+	 * elsewhere.
+	 */
+	if (!__access_ok(pc, instructions_to_print * sizeof(int), USER_DS)) {
+		pr_info("%s[%d]: Bad NIP, not dumping instructions.\n",
+			current->comm, current->pid);
+		return;
+	}
+

This will conflict with my serie 
https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=64611 
which changes instructions_to_print to a constant. Will you merge it or 
do you expect me to rebase my serie ?

I can fix it up.

But I see you've already rebased it and resent, you're too quick for me :)

cheers