Patch "um: Fix PTRACE_POKEUSER on x86_64" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

um: Fix PTRACE_POKEUSER on x86_64

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     um-fix-ptrace_pokeuser-on-x86_64.patch

and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Richard Weinberger <[email protected]>
Date: Sat, 1 Apr 2017 00:41:57 +0200
Subject: um: Fix PTRACE_POKEUSER on x86_64

From: Richard Weinberger <[email protected]>

commit 9abc74a22d85ab29cef9896a2582a530da7e79bf upstream.

This is broken since ever but sadly nobody noticed. Recent versions of GDB set DR_CONTROL unconditionally and UML dies due to a heap corruption. It turns out that the PTRACE_POKEUSER was copy&pasted from i386 and assumes that addresses are 4 bytes long.

Fix that by using 8 as address size in the calculation.

---
 arch/x86/um/ptrace_64.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -125,7 +125,7 @@ int poke_user(struct task_struct *child,
 	else if ((addr >= offsetof(struct user, u_debugreg[0])) &&
 		(addr <= offsetof(struct user, u_debugreg[7]))) {
 		addr -= offsetof(struct user, u_debugreg[0]);
-		addr = addr >> 2;
+		addr = addr >> 3;
 		if ((addr == 4) || (addr == 5))
 			return -EIO;
 		child->thread.arch.debugregs[addr] = data;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/um-fix-ptrace_pokeuser-on-x86_64.patch