linux-kernel - [PATCH] mm/memory: Avoid unnecessary kernel/user pointer conversion

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Message-Id: <20210914150820.19326-1-amit.kachhap@arm.com>
Date:   Tue, 14 Sep 2021 20:38:20 +0530
From:   Amit Daniel Kachhap <amit.kachhap@....com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org,
        Vincenzo Frascino <Vincenzo.Frascino@....com>,
        Amit Daniel Kachhap <amit.kachhap@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] mm/memory: Avoid unnecessary kernel/user pointer conversion

Annotating a pointer from __user to kernel and then back again might
confuse sparse. In copy_huge_page_from_user() it can be avoided by
removing the intermediate variable since it is never used.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
---
 mm/memory.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 25fc46e87214..90970d19b7dd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5411,7 +5411,6 @@ long copy_huge_page_from_user(struct page *dst_page,
 				unsigned int pages_per_huge_page,
 				bool allow_pagefault)
 {
-	void *src = (void *)usr_src;
 	void *page_kaddr;
 	unsigned long i, rc = 0;
 	unsigned long ret_val = pages_per_huge_page * PAGE_SIZE;
@@ -5424,8 +5423,7 @@ long copy_huge_page_from_user(struct page *dst_page,
 		else
 			page_kaddr = kmap_atomic(subpage);
 		rc = copy_from_user(page_kaddr,
-				(const void __user *)(src + i * PAGE_SIZE),
-				PAGE_SIZE);
+				usr_src + i * PAGE_SIZE, PAGE_SIZE);
 		if (allow_pagefault)
 			kunmap(subpage);
 		else
-- 
2.17.1