[PATCH 4.9 11/16] metag/ptrace: Preserve previous registers for short regset write

[Greg Kroah-Hartman]

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

------------------

From: Dave Martin <Dave.Martin@xxxxxxx>

commit a78ce80d2c9178351b34d78fec805140c29c193e upstream.

Ensure that if userspace supplies insufficient data to PTRACE_SETREGSET
to fill all the registers, the thread's old registers are preserved.

Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
Acked-by: James Hogan <james.hogan@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/metag/kernel/ptrace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/metag/kernel/ptrace.c
+++ b/arch/metag/kernel/ptrace.c
@@ -303,7 +303,7 @@ static int metag_tls_set(struct task_str
 			const void *kbuf, const void __user *ubuf)
 {
 	int ret;
-	void __user *tls;
+	void __user *tls = target->thread.tls_ptr;
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &tls, 0, -1);
 	if (ret)