Check return value of putreg in PTRACE_SETREGS

This means if an illegal value is set for the segment registers there
ptrace will error out now with an errno instead of silently ignoring
it.

Signed-off-by: Andi Kleen <ak@suse.de>

---
 arch/x86_64/kernel/ptrace.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Index: linux/arch/x86_64/kernel/ptrace.c
===================================================================
--- linux.orig/arch/x86_64/kernel/ptrace.c
+++ linux/arch/x86_64/kernel/ptrace.c
@@ -536,8 +536,12 @@ long arch_ptrace(struct task_struct *chi
 		}
 		ret = 0;
 		for (ui = 0; ui < sizeof(struct user_regs_struct); ui += sizeof(long)) {
-			ret |= __get_user(tmp, (unsigned long __user *) data);
-			putreg(child, ui, tmp);
+			ret = __get_user(tmp, (unsigned long __user *) data);
+			if (ret)
+				break;
+			ret = putreg(child, ui, tmp);
+			if (ret)
+				break;
 			data += sizeof(long);
 		}
 		break;