arm64/ptrace: Preserve previous registers for short regset write

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@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>
[sw0312.kim: backport linux-4.9.y stable commit for better compat ptrace]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Change-Id: I1de80715bf95f909290dd04546d8cd6eb2413598

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index ca501270219c1f193da03f61951d6f1f78d74c08..185dd69e44c120d3dbd35a1f7f535fc533eeccb6 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -489,7 +489,7 @@ static int gpr_set(struct task_struct *target, const struct user_regset *regset,
                   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)
@@ -519,7 +519,8 @@ static int fpr_set(struct task_struct *target, const struct user_regset *regset,
                   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)
@@ -543,7 +544,7 @@ static int tls_set(struct task_struct *target, const struct user_regset *regset,
                   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)