x86/fpu: Use fpstate::size

Make use of fpstate::size in various places which require the buffer size
information for sanity checks or memcpy() sizing.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211013145322.973518954@linutronix.de

arch/x86/kernel/fpu/core.c

@@ -166,13 +166,12 @@ void fpu_swap_kvm_fpu(struct fpu *save, struct fpu *rstor, u64 restore_mask)
 	fpregs_lock();
 
 	if (save) {
-		if (test_thread_flag(TIF_NEED_FPU_LOAD)) {
-			memcpy(&save->fpstate->regs,
-			       &current->thread.fpu.fpstate->regs,
-			       fpu_kernel_xstate_size);
-		} else {
+		struct fpstate *fpcur = current->thread.fpu.fpstate;
+
+		if (test_thread_flag(TIF_NEED_FPU_LOAD))
+			memcpy(&save->fpstate->regs, &fpcur->regs, fpcur->size);
+		else
 			save_fpregs_to_fpstate(save);
-		}
 	}
 
 	if (rstor) {
@@ -398,7 +397,7 @@ int fpu_clone(struct task_struct *dst)
 	fpregs_lock();
 	if (test_thread_flag(TIF_NEED_FPU_LOAD)) {
 		memcpy(&dst_fpu->fpstate->regs, &src_fpu->fpstate->regs,
-		       fpu_kernel_xstate_size);
+		       dst_fpu->fpstate->size);
 	} else {
 		save_fpregs_to_fpstate(dst_fpu);
 	}

arch/x86/kernel/fpu/signal.c

@@ -313,15 +313,13 @@ static bool restore_fpregs_from_user(void __user *buf, u64 xrestore,
 static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
 			      bool ia32_fxstate)
 {
-	int state_size = fpu_kernel_xstate_size;
 	struct task_struct *tsk = current;
 	struct fpu *fpu = &tsk->thread.fpu;
 	struct user_i387_ia32_struct env;
+	bool success, fx_only = false;
 	union fpregs_state *fpregs;
+	unsigned int state_size;
 	u64 user_xfeatures = 0;
-	bool fx_only = false;
-	bool success;
-
 
 	if (use_xsave()) {
 		struct _fpx_sw_bytes fx_sw_user;
@@ -334,6 +332,7 @@ static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
 		user_xfeatures = fx_sw_user.xfeatures;
 	} else {
 		user_xfeatures = XFEATURE_MASK_FPSSE;
+		state_size = fpu->fpstate->size;
 	}
 
 	if (likely(!ia32_fxstate)) {