arm64/ptrace: Avoid uninitialised struct padding in fpr_set()

commit aeb1f39d upstream.

This patch adds an explicit __reserved[] field to user_fpsimd_state
to replace what was previously unnamed padding.

This ensures that data in this region are propagated across
assignment rather than being left possibly uninitialised at the
destination.

Fixes: 60ffc30d ("arm64: Exception handling")
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: Ben Hutchings <ben@decadent.org.uk>

arch/arm64/include/uapi/asm/ptrace.h

@@ -75,6 +75,7 @@ struct user_fpsimd_state {
 	__uint128_t	vregs[32];
 	__u32		fpsr;
 	__u32		fpcr;
+	__u32		__reserved[2];
 };
 
 struct user_hwdebug_state {