linux-kernel - [PATCH 3.2 115/152] ppc32: fix copy_from

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Message-ID: <lsq.1479082447.45063792@decadent.org.uk>
Date:   Mon, 14 Nov 2016 00:14:07 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Al Viro" <viro@...iv.linux.org.uk>
Subject: [PATCH 3.2 115/152] ppc32: fix copy_from_user()

3.2.84-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Al Viro <viro@...iv.linux.org.uk>

commit 224264657b8b228f949b42346e09ed8c90136a8e upstream.

should clear on access_ok() failures.  Also remove the useless
range truncation logics.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
[bwh: Backported to 3.2: no calls to check_object_size()]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -332,30 +332,17 @@ extern unsigned long __copy_tofrom_user(
 static inline unsigned long copy_from_user(void *to,
 		const void __user *from, unsigned long n)
 {
-	unsigned long over;
-
-	if (access_ok(VERIFY_READ, from, n))
+	if (likely(access_ok(VERIFY_READ, from, n)))
 		return __copy_tofrom_user((__force void __user *)to, from, n);
-	if ((unsigned long)from < TASK_SIZE) {
-		over = (unsigned long)from + n - TASK_SIZE;
-		return __copy_tofrom_user((__force void __user *)to, from,
-				n - over) + over;
-	}
+	memset(to, 0, n);
 	return n;
 }
 
 static inline unsigned long copy_to_user(void __user *to,
 		const void *from, unsigned long n)
 {
-	unsigned long over;
-
 	if (access_ok(VERIFY_WRITE, to, n))
 		return __copy_tofrom_user(to, (__force void __user *)from, n);
-	if ((unsigned long)to < TASK_SIZE) {
-		over = (unsigned long)to + n - TASK_SIZE;
-		return __copy_tofrom_user(to, (__force void __user *)from,
-				n - over) + over;
-	}
 	return n;
 }
 
@@ -446,10 +433,6 @@ static inline unsigned long clear_user(v
 	might_sleep();
 	if (likely(access_ok(VERIFY_WRITE, addr, size)))
 		return __clear_user(addr, size);
-	if ((unsigned long)addr < TASK_SIZE) {
-		unsigned long over = (unsigned long)addr + size - TASK_SIZE;
-		return __clear_user(addr, size - over) + over;
-	}
 	return size;
 }