3.13.11-ckt34 -stable review patch.  If anyone has any objections, please let 
me know.

---8<------------------------------------------------------------

From: John Blackwood <[email protected]>

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 <[email protected]>
[will: added comment to justify why this is in the arch code]
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Kamal Mostafa <[email protected]>
---
 arch/arm64/kernel/ptrace.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index b1269da..bfe4a42 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -51,6 +51,12 @@
  */
 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
-- 
1.9.1

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