Patch "s390/ptrace: Preserve previous registers for short regset write" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

s390/ptrace: Preserve previous registers for short regset write

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
s390-ptrace-preserve-previous-registers-for-short-regset-write.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Martin Schwidefsky <[email protected]>
Date: Tue, 24 Jan 2017 08:05:52 +0100
Subject: s390/ptrace: Preserve previous registers for short regset write

From: Martin Schwidefsky <[email protected]>

commit 9dce990d2cf57b5ed4e71a9cdbd7eae4335111ff upstream.

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

convert_vx_to_fp() is adapted to handle only a specified number of registers rather than unconditionally handling all of them: other callers of this function are adapted appropriately.

Based on an initial patch by Dave Martin.

---
 arch/s390/kernel/ptrace.c |    8 ++++++++
 1 file changed, 8 insertions(+)

@@ -963,6 +963,11 @@ static int s390_fpregs_set(struct task_s
 	if (target == current)
 		save_fpu_regs();
 
+	if (MACHINE_HAS_VX)
+		convert_vx_to_fp(fprs, target->thread.fpu.vxrs);
+	else
+		memcpy(&fprs, target->thread.fpu.fprs, sizeof(fprs));
+
 	/* If setting FPC, must validate it first. */
 	if (count > 0 && pos < offsetof(s390_fp_regs, fprs)) {
 		u32 ufpc[2] = { target->thread.fpu.fpc, 0 };

@@ -1067,6 +1072,9 @@ static int s390_vxrs_low_set(struct task
 	if (target == current)
 		save_fpu_regs();
 
+	for (i = 0; i < __NUM_VXRS_LOW; i++)
+		vxrs[i] = *((__u64 *)(target->thread.fpu.vxrs + i) + 1);
+
 	rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vxrs, 0, -1);
 	if (rc == 0)
 		for (i = 0; i < __NUM_VXRS_LOW; i++)

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/s390-ptrace-preserve-previous-registers-for-short-regset-write.patch