From: Dave Martin <Dave.Martin@arm.com>
Date: Wed, 18 Jan 2017 16:25:21 +0000 (+0000)
Subject: arm64/ptrace: Preserve previous registers for short regset write - 2
X-Git-Tag: firefly_0821_release~176^2~4^2~2^2~36
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d8263f1753ce362638760e66065c55a7136698eb;p=firefly-linux-kernel-4.4.55.git

arm64/ptrace: Preserve previous registers for short regset write - 2

commit 9dd73f72f218320c6c90da5f834996e7360dc227 upstream.

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

Fixes: 766a85d7bc5d ("arm64: ptrace: add NT_ARM_SYSTEM_CALL regset")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Will Deacon <Will.Deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 29d15fdcdae3..ba24db88d54e 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -576,7 +576,8 @@ static int system_call_set(struct task_struct *target,
 			   unsigned int pos, unsigned int count,
 			   const void *kbuf, const void __user *ubuf)
 {
-	int syscallno, ret;
+	int syscallno = task_pt_regs(target)->syscallno;
+	int ret;
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &syscallno, 0, -1);
 	if (ret)