linux-kernel - [PATCH 3.16 236/370] arm64/ptrace: Preserve previous registers for short regset write

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Message-ID: <lsq.1489146383.568755484@decadent.org.uk>
Date:   Fri, 10 Mar 2017 11:46:23 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Will Deacon" <Will.Deacon@....com>,
        "Catalin Marinas" <catalin.marinas@....com>,
        "Dave Martin" <Dave.Martin@....com>
Subject: [PATCH 3.16 236/370] arm64/ptrace: Preserve previous registers
 for short regset write

3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Dave Martin <Dave.Martin@....com>

commit 9a17b876b573441bfb3387ad55d98bf7184daf9d upstream.

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

Fixes: 478fcb2cdb23 ("arm64: Debugging support")
Signed-off-by: Dave Martin <Dave.Martin@....com>
Acked-by: Will Deacon <Will.Deacon@....com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm64/kernel/ptrace.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -491,7 +491,7 @@ static int gpr_set(struct task_struct *t
 		   const void *kbuf, const void __user *ubuf)
 {
 	int ret;
-	struct user_pt_regs newregs;
+	struct user_pt_regs newregs = task_pt_regs(target)->user_regs;
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newregs, 0, -1);
 	if (ret)
@@ -521,7 +521,8 @@ static int fpr_set(struct task_struct *t
 		   const void *kbuf, const void __user *ubuf)
 {
 	int ret;
-	struct user_fpsimd_state newstate;
+	struct user_fpsimd_state newstate =
+		target->thread.fpsimd_state.user_fpsimd;
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newstate, 0, -1);
 	if (ret)
@@ -545,7 +546,7 @@ static int tls_set(struct task_struct *t
 		   const void *kbuf, const void __user *ubuf)
 {
 	int ret;
-	unsigned long tls;
+	unsigned long tls = target->thread.tp_value;
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &tls, 0, -1);
 	if (ret)