Commit bb521c5d authored Sep 23, 2009 by Nikanth Karthikesan Committed by Linus Torvalds Sep 24, 2009

/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>

parent 0b8c78f2

drivers/char/mem.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;