linux-kernel - [PATCH 1/8] scatterlist: make sure sg_miter_next() doesn't return 0 sized mappings

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Message-Id: <1238583884-13517-2-git-send-email-tj@kernel.org>
Date:	Wed,  1 Apr 2009 20:04:37 +0900
From:	Tejun Heo <tj@...nel.org>
To:	axboe@...nel.dk, bharrosh@...asas.com, linux-kernel@...r.kernel.org
Cc:	Tejun Heo <tj@...nel.org>
Subject: [PATCH 1/8] scatterlist: make sure sg_miter_next() doesn't return 0 sized mappings

Impact: fix not-so-critical but annoying bug

sg_miter_next() returns 0 sized mapping if there is an zero sized sg
entry in the list or at the end of each iteration.  As the users
always check the ->length field, this bug shouldn't be critical other
than causing unnecessary iteration.

Fix it.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 lib/scatterlist.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index b7b449d..a295e40 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -347,9 +347,12 @@ bool sg_miter_next(struct sg_mapping_iter *miter)
 	sg_miter_stop(miter);
 
 	/* get to the next sg if necessary.  __offset is adjusted by stop */
-	if (miter->__offset == miter->__sg->length && --miter->__nents) {
-		miter->__sg = sg_next(miter->__sg);
-		miter->__offset = 0;
+	while (miter->__offset == miter->__sg->length) {
+		if (--miter->__nents) {
+			miter->__sg = sg_next(miter->__sg);
+			miter->__offset = 0;
+		} else
+			return false;
 	}
 
 	/* map the next page */
-- 
1.6.0.2

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