Patch "arm64: Clear out any singlestep state on a ptrace detach operation" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    arm64: Clear out any singlestep state on a ptrace detach operation

to the 4.4-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:
     arm64-clear-out-any-singlestep-state-on-a-ptrace-detach-operation.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 5db4fd8c52810bd9740c1240ebf89223b171aa70 Mon Sep 17 00:00:00 2001
From: John Blackwood <john.blackwood@ccur.com>
Date: Mon, 7 Dec 2015 11:50:34 +0000
Subject: arm64: Clear out any singlestep state on a ptrace detach operation

From: John Blackwood <john.blackwood@ccur.com>

commit 5db4fd8c52810bd9740c1240ebf89223b171aa70 upstream.

Make sure to clear out any ptrace singlestep state when a ptrace(2)
PTRACE_DETACH call is made on arm64 systems.

Otherwise, the previously ptraced task will die off with a SIGTRAP
signal if the debugger just previously singlestepped the ptraced task.

Signed-off-by: John Blackwood <john.blackwood@ccur.com>
[will: added comment to justify why this is in the arch code]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/kernel/ptrace.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -58,6 +58,12 @@
  */
 void ptrace_disable(struct task_struct *child)
 {
+	/*
+	 * This would be better off in core code, but PTRACE_DETACH has
+	 * grown its fair share of arch-specific worts and changing it
+	 * is likely to cause regressions on obscure architectures.
+	 */
+	user_disable_single_step(child);
 }
 
 #ifdef CONFIG_HAVE_HW_BREAKPOINT


Patches currently in stable-queue which might be from john.blackwood@ccur.com are

queue-4.4/arm64-clear-out-any-singlestep-state-on-a-ptrace-detach-operation.patch