[PATCH 3.10 48/53] arm64: Clear out any singlestep state on a ptrace detach operation

From: Greg Kroah-Hartman
Date: Wed Jan 27 2016 - 14:56:43 EST

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


From: John Blackwood <john.blackwood@xxxxxxxx>

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@xxxxxxxx>
[will: added comment to justify why this is in the arch code]
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- 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);