linux-kernel - [PATCH 4.14 06/62] ARM: 8790/1: signal: always use __copy_to

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Date:   Mon, 18 Feb 2019 14:43:12 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Julien Thierry <julien.thierry@....com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        "David A. Long" <dave.long@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 06/62] ARM: 8790/1: signal: always use __copy_to_user to save iwmmxt context

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Reviewed-by: Julien Thierry <julien.thierry@....com>
Signed-off-by: Sasha Levin <sashal@...nel.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 1dc1f39825b6..b12499cc3582 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -76,8 +76,6 @@ 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
@@ -85,10 +83,14 @@ 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;
 }
 
-- 
2.19.1