linux-kernel - [PATCH 4.19 02/17] ARM: 8790/1: signal: always use __copy_to

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Date:   Wed, 13 Feb 2019 16:32:08 -0500
From:   David Long <dave.long@...aro.org>
To:     stable@...r.kernel.org,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Florian Fainelli <f.fainelli@...il.com>,
        Julien Thierry <julien.thierry@....com>,
        Tony Lindgren <tony@...mide.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     Will Deacon <will.deacon@....com>, Mark Brown <broonie@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 4.19 02/17] ARM: 8790/1: signal: always use __copy_to_user to save iwmmxt context

From: Julien Thierry <julien.thierry@....com>

Commit 73839798af7ebc6c8d0c9271ebbbc148700e521f upstream.

When setting a dummy iwmmxt context, create a local instance and
use __copy_to_user both cases whether iwmmxt is being used or not.
This has the benefit of disabling/enabling PAN once for the whole copy
intead of once per write.

Signed-off-by: Julien Thierry <julien.thierry@....com>
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: David A. Long <dave.long@...aro.org>
---
 arch/arm/kernel/signal.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 76fe75d36312..464393d241e1 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -77,8 +77,6 @@ static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
 		kframe->magic = IWMMXT_MAGIC;
 		kframe->size = IWMMXT_STORAGE_SIZE;
 		iwmmxt_task_copy(current_thread_info(), &kframe->storage);
-
-		err = __copy_to_user(frame, kframe, sizeof(*frame));
 	} else {
 		/*
 		 * For bug-compatibility with older kernels, some space
@@ -86,10 +84,14 @@ static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
 		 * Set the magic and size appropriately so that properly
 		 * written userspace can skip it reliably:
 		 */
-		__put_user_error(DUMMY_MAGIC, &frame->magic, err);
-		__put_user_error(IWMMXT_STORAGE_SIZE, &frame->size, err);
+		*kframe = (struct iwmmxt_sigframe) {
+			.magic = DUMMY_MAGIC,
+			.size  = IWMMXT_STORAGE_SIZE,
+		};
 	}
 
+	err = __copy_to_user(frame, kframe, sizeof(*kframe));
+
 	return err;
 }
 
-- 
2.17.1