metag/ptrace: Preserve previous registers for short regset write

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@arm.com>
Acked-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/metag/kernel/ptrace.c b/arch/metag/kernel/ptrace.c
index 7563628..ae659ba 100644 (file)
--- a/arch/metag/kernel/ptrace.c
+++ b/arch/metag/kernel/ptrace.c
@@ -303,7 +303,7 @@ static int metag_tls_set(struct task_struct *target,
                        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)