linux-kernel - [PATCH] mm: gup: fix access

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Date:   Fri, 21 Apr 2017 18:26:32 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Ingo Molnar <mingo@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mm: gup: fix access_ok() argument type

MIPS just got changed to only accept a pointer argument for access_ok(),
causing one warning in drivers/scsi/pmcraid.c. I tried changing x86
the same way and found the same warning in __get_user_pages_fast()
and nowhere else in the kernel during randconfig testing:

mm/gup.c: In function '__get_user_pages_fast':
mm/gup.c:1578:6: error: passing argument 1 of '__chk_range_not_ok' makes pointer from integer without a cast [-Werror=int-conversion]

It would probably be a good idea to enforce type-safety in general,
so let's change this file to not cause a warning if we do that.

I don't know why the warning did not appear on MIPS.

Fixes: 2667f50e8b81 ("mm: introduce a general RCU get_user_pages_fast()")
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 mm/gup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index 2559a3987de7..7f5bc26d9229 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1575,7 +1575,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 	end = start + len;
 
 	if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
-					start, len)))
+					(void __user *)start, len)))
 		return 0;
 
 	/*
-- 
2.9.0