1 files changed, 106 insertions, 51 deletions

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 400a05e1c1c5..a4ec65317a7f 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -170,14 +170,15 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
 			 IS_ENABLED(CONFIG_IA32_EMULATION));
 
+	if (!static_cpu_has(X86_FEATURE_FPU)) {
+		struct user_i387_ia32_struct fp;
+		fpregs_soft_get(current, NULL, (struct membuf){.p = &fp,
+						.left = sizeof(fp)});
+		return copy_to_user(buf, &fp, sizeof(fp)) ? -EFAULT : 0;
+	}
+
 	if (!access_ok(buf, size))
 		return -EACCES;
-
-	if (!static_cpu_has(X86_FEATURE_FPU))
-		return fpregs_soft_get(current, NULL, 0,
-			sizeof(struct user_i387_ia32_struct), NULL,
-			(struct _fpstate_32 __user *) buf) ? -1 : 1;
-
 retry:
 	/*
 	 * Load the FPU registers if they are not valid for the current task.
@@ -211,9 +212,9 @@ retry:
 }
 
 static inline void
-sanitize_restored_xstate(union fpregs_state *state,
-			 struct user_i387_ia32_struct *ia32_env,
-			 u64 xfeatures, int fx_only)
+sanitize_restored_user_xstate(union fpregs_state *state,
+			      struct user_i387_ia32_struct *ia32_env,
+			      u64 user_xfeatures, int fx_only)
 {
 	struct xregs_state *xsave = &state->xsave;
 	struct xstate_header *header = &xsave->header;
@@ -226,13 +227,22 @@ sanitize_restored_xstate(union fpregs_state *state,
 		 */
 
 		/*
-		 * Init the state that is not present in the memory
-		 * layout and not enabled by the OS.
+		 * 'user_xfeatures' might have bits clear which are
+		 * set in header->xfeatures. This represents features that
+		 * were in init state prior to a signal delivery, and need
+		 * to be reset back to the init state.  Clear any user
+		 * feature bits which are set in the kernel buffer to get
+		 * them back to the init state.
+		 *
+		 * Supervisor state is unchanged by input from userspace.
+		 * Ensure supervisor state bits stay set and supervisor
+		 * state is not modified.
 		 */
 		if (fx_only)
 			header->xfeatures = XFEATURE_MASK_FPSSE;
 		else
-			header->xfeatures &= xfeatures;
+			header->xfeatures &= user_xfeatures |
+					     xfeatures_mask_supervisor();
 	}
 
 	if (use_fxsr()) {
@@ -252,16 +262,24 @@ sanitize_restored_xstate(union fpregs_state *state,
  */
 static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
 {
+	u64 init_bv;
+	int r;
+
 	if (use_xsave()) {
 		if (fx_only) {
-			u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
-			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-			return copy_user_to_fxregs(buf);
+			init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
+
+			r = copy_user_to_fxregs(buf);
+			if (!r)
+				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+			return r;
 		} else {
-			u64 init_bv = xfeatures_mask & ~xbv;
-			if (unlikely(init_bv))
+			init_bv = xfeatures_mask_user() & ~xbv;
+
+			r = copy_user_to_xregs(buf, xbv);
+			if (!r && unlikely(init_bv))
 				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-			return copy_user_to_xregs(buf, xbv);
+			return r;
 		}
 	} else if (use_fxsr()) {
 		return copy_user_to_fxregs(buf);
@@ -277,7 +295,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 	struct task_struct *tsk = current;
 	struct fpu *fpu = &tsk->thread.fpu;
 	struct user_i387_ia32_struct env;
-	u64 xfeatures = 0;
+	u64 user_xfeatures = 0;
 	int fx_only = 0;
 	int ret = 0;
 
@@ -285,7 +303,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 			 IS_ENABLED(CONFIG_IA32_EMULATION));
 
 	if (!buf) {
-		fpu__clear(fpu);
+		fpu__clear_user_states(fpu);
 		return 0;
 	}
 
@@ -310,32 +328,14 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 			trace_x86_fpu_xstate_check_failed(fpu);
 		} else {
 			state_size = fx_sw_user.xstate_size;
-			xfeatures = fx_sw_user.xfeatures;
+			user_xfeatures = fx_sw_user.xfeatures;
 		}
 	}
 
-	/*
-	 * The current state of the FPU registers does not matter. By setting
-	 * TIF_NEED_FPU_LOAD unconditionally it is ensured that the our xstate
-	 * is not modified on context switch and that the xstate is considered
-	 * to be loaded again on return to userland (overriding last_cpu avoids
-	 * the optimisation).
-	 */
-	set_thread_flag(TIF_NEED_FPU_LOAD);
-	__fpu_invalidate_fpregs_state(fpu);
-
 	if ((unsigned long)buf_fx % 64)
 		fx_only = 1;
-	/*
-	 * For 32-bit frames with fxstate, copy the fxstate so it can be
-	 * reconstructed later.
-	 */
-	if (ia32_fxstate) {
-		ret = __copy_from_user(&env, buf, sizeof(env));
-		if (ret)
-			goto err_out;
-		envp = &env;
-	} else {
+
+	if (!ia32_fxstate) {
 		/*
 		 * Attempt to restore the FPU registers directly from user
 		 * memory. For that to succeed, the user access cannot cause
@@ -345,20 +345,65 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		 */
 		fpregs_lock();
 		pagefault_disable();
-		ret = copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only);
+		ret = copy_user_to_fpregs_zeroing(buf_fx, user_xfeatures, fx_only);
 		pagefault_enable();
 		if (!ret) {
+
+			/*
+			 * Restore supervisor states: previous context switch
+			 * etc has done XSAVES and saved the supervisor states
+			 * in the kernel buffer from which they can be restored
+			 * now.
+			 *
+			 * We cannot do a single XRSTORS here - which would
+			 * be nice - because the rest of the FPU registers are
+			 * being restored from a user buffer directly. The
+			 * single XRSTORS happens below, when the user buffer
+			 * has been copied to the kernel one.
+			 */
+			if (test_thread_flag(TIF_NEED_FPU_LOAD) &&
+			    xfeatures_mask_supervisor())
+				copy_kernel_to_xregs(&fpu->state.xsave,
+						     xfeatures_mask_supervisor());
 			fpregs_mark_activate();
 			fpregs_unlock();
 			return 0;
 		}
-		fpregs_deactivate(fpu);
 		fpregs_unlock();
+	} else {
+		/*
+		 * For 32-bit frames with fxstate, copy the fxstate so it can
+		 * be reconstructed later.
+		 */
+		ret = __copy_from_user(&env, buf, sizeof(env));
+		if (ret)
+			goto err_out;
+		envp = &env;
 	}
 
+	/*
+	 * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is
+	 * not modified on context switch and that the xstate is considered
+	 * to be loaded again on return to userland (overriding last_cpu avoids
+	 * the optimisation).
+	 */
+	fpregs_lock();
+
+	if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
+
+		/*
+		 * Supervisor states are not modified by user space input.  Save
+		 * current supervisor states first and invalidate the FPU regs.
+		 */
+		if (xfeatures_mask_supervisor())
+			copy_supervisor_to_kernel(&fpu->state.xsave);
+		set_thread_flag(TIF_NEED_FPU_LOAD);
+	}
+	__fpu_invalidate_fpregs_state(fpu);
+	fpregs_unlock();
 
 	if (use_xsave() && !fx_only) {
-		u64 init_bv = xfeatures_mask & ~xfeatures;
+		u64 init_bv = xfeatures_mask_user() & ~user_xfeatures;
 
 		if (using_compacted_format()) {
 			ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
@@ -366,17 +411,24 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 			ret = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
 
 			if (!ret && state_size > offsetof(struct xregs_state, header))
-				ret = validate_xstate_header(&fpu->state.xsave.header);
+				ret = validate_user_xstate_header(&fpu->state.xsave.header);
 		}
 		if (ret)
 			goto err_out;
 
-		sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
+		sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
+					      fx_only);
 
 		fpregs_lock();
 		if (unlikely(init_bv))
 			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-		ret = copy_kernel_to_xregs_err(&fpu->state.xsave, xfeatures);
+
+		/*
+		 * Restore previously saved supervisor xstates along with
+		 * copied-in user xstates.
+		 */
+		ret = copy_kernel_to_xregs_err(&fpu->state.xsave,
+					       user_xfeatures | xfeatures_mask_supervisor());
 
 	} else if (use_fxsr()) {
 		ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
@@ -385,11 +437,14 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 			goto err_out;
 		}
 
-		sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
+		sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
+					      fx_only);
 
 		fpregs_lock();
 		if (use_xsave()) {
-			u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
+			u64 init_bv;
+
+			init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
 			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
 		}
 
@@ -410,7 +465,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 
 err_out:
 	if (ret)
-		fpu__clear(fpu);
+		fpu__clear_user_states(fpu);
 	return ret;
 }
 
@@ -465,7 +520,7 @@ void fpu__init_prepare_fx_sw_frame(void)
 
 	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
 	fx_sw_reserved.extended_size = size;
-	fx_sw_reserved.xfeatures = xfeatures_mask;
+	fx_sw_reserved.xfeatures = xfeatures_mask_user();
 	fx_sw_reserved.xstate_size = fpu_user_xstate_size;
 
 	if (IS_ENABLED(CONFIG_IA32_EMULATION) ||