linux-kernel - [PATCH 4.4 08/23] s390/ptrace: Preserve previous registers for short regset write

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Message-Id: <20170131053625.291556420@linuxfoundation.org>
Date:   Tue, 31 Jan 2017 06:37:10 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dave Martin <Dave.Martin@....com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: [PATCH 4.4 08/23] s390/ptrace: Preserve previous registers for short regset write

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

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

From: Martin Schwidefsky <schwidefsky@...ibm.com>

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.

Reported-by: Dave Martin <Dave.Martin@....com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -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++)