arm64/ptrace: Preserve previous registers for short regset write

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

Cc: <stable@vger.kernel.org> # 3.7.x-
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>

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index fc35e06..8c0bc34 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -596,7 +596,7 @@ 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)
@@ -626,7 +626,8 @@ 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)
@@ -650,7 +651,7 @@ 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)