From: Nikanth Karthikesan <knikanth@suse.de>
Date: Wed, 23 Sep 2009 22:57:09 +0000 (-0700)
Subject: /dev/zero: avoid repeated access_ok() checks
X-Git-Tag: v3.0~7422
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=bb521c5de070b86a1e049e2dbf62328f717ff1e8;p=platform%2Fkernel%2Flinux-amlogic.git

/dev/zero: avoid repeated access_ok() checks

In read_zero, we check for access_ok() once for the count bytes.  It is
unnecessarily checked again in clear_user.  Use __clear_user, which does
not check for access_ok().

Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 0aede1d..6c8b65d 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -690,7 +690,7 @@ static ssize_t read_zero(struct file * file, char __user * buf,
 
 		if (chunk > PAGE_SIZE)
 			chunk = PAGE_SIZE;	/* Just for latency reasons */
-		unwritten = clear_user(buf, chunk);
+		unwritten = __clear_user(buf, chunk);
 		written += chunk - unwritten;
 		if (unwritten)
 			break;