[PATCH 4.14 64/88] x86/fpu: Reset state for all signal restore failures

[Sasha Levin <sashal@kernel.org>]

From: Thomas Gleixner <tglx@linutronix.de>

commit efa165504943f2128d50f63de0c02faf6dcceb0d upstream.

If access_ok() or fpregs_soft_set() fails in __fpu__restore_sig() then the
function just returns but does not clear the FPU state as it does for all
other fatal failures.

Clear the FPU state for these failures as well.

Fixes: 72a671ced66d ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/87mtryyhhz.ffs@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kernel/fpu/signal.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index d99a8ee9e185..86a231338bbf 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -272,6 +272,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 	int state_size = fpu_kernel_xstate_size;
 	u64 xfeatures = 0;
 	int fx_only = 0;
+	int ret = 0;
 
 	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
 			 IS_ENABLED(CONFIG_IA32_EMULATION));
@@ -281,15 +282,21 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		return 0;
 	}
 
-	if (!access_ok(VERIFY_READ, buf, size))
-		return -EACCES;
+	if (!access_ok(VERIFY_READ, buf, size)) {
+		ret = -EACCES;
+		goto out_err;
+	}
 
 	fpu__initialize(fpu);
 
-	if (!static_cpu_has(X86_FEATURE_FPU))
-		return fpregs_soft_set(current, NULL,
-				       0, sizeof(struct user_i387_ia32_struct),
-				       NULL, buf) != 0;
+	if (!static_cpu_has(X86_FEATURE_FPU)) {
+		ret = fpregs_soft_set(current, NULL,
+				      0, sizeof(struct user_i387_ia32_struct),
+				      NULL, buf) != 0;
+		if (ret)
+			goto out_err;
+		return 0;
+	}
 
 	if (use_xsave()) {
 		struct _fpx_sw_bytes fx_sw_user;
@@ -349,6 +356,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		fpu__restore(fpu);
 		local_bh_enable();
 
+		/* Failure is already handled */
 		return err;
 	} else {
 		/*
@@ -356,13 +364,14 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		 * state to the registers directly (with exceptions handled).
 		 */
 		user_fpu_begin();
-		if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
-			fpu__clear(fpu);
-			return -1;
-		}
+		if (!copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only))
+			return 0;
+		ret = -1;
 	}
 
-	return 0;
+out_err:
+	fpu__clear(fpu);
+	return ret;
 }
 
 static inline int xstate_sigframe_size(void)
-- 
2.30.2