linux-kernel - [PATCH 3/6] lib/scatterlist: Do not leak pages when high-order allocation fails

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Date:   Wed,  7 Mar 2018 12:47:09 +0000
From:   Tvrtko Ursulin <tursulin@...ulin.net>
To:     linux-kernel@...r.kernel.org
Cc:     Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Bart Van Assche <bart.vanassche@....com>,
        Hannes Reinecke <hare@...e.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 3/6] lib/scatterlist: Do not leak pages when high-order allocation fails

From: Tvrtko Ursulin <tvrtko.ursulin@...el.com>

If a higher-order allocation fails, the existing abort and cleanup path
would consider all segments allocated so far as 0-order page allocations
and would therefore leak memory.

Fix this by cleaning up using sgl_free_n_order which allows the correct
page order to be passed in.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Cc: Bart Van Assche <bart.vanassche@....com>
Cc: Hannes Reinecke <hare@...e.com>
Cc: Johannes Thumshirn <jthumshirn@...e.de>
Cc: Jens Axboe <axboe@...nel.dk>
---
 lib/scatterlist.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 9884be50a2c0..e13a759c5c49 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -493,7 +493,7 @@ struct scatterlist *sgl_alloc_order(unsigned long length, unsigned int order,
 {
 	unsigned int chunk_len = PAGE_SIZE << order;
 	struct scatterlist *sgl, *sg;
-	unsigned int nent;
+	unsigned int nent, i;
 
 	nent = round_up(length, chunk_len) >> (PAGE_SHIFT + order);
 
@@ -517,11 +517,12 @@ struct scatterlist *sgl_alloc_order(unsigned long length, unsigned int order,
 
 	sg_init_table(sgl, nent);
 	sg = sgl;
+	i = 0;
 	while (length) {
 		struct page *page = alloc_pages(gfp, order);
 
 		if (!page) {
-			sgl_free(sgl);
+			sgl_free_n_order(sgl, i, order);
 			return NULL;
 		}
 
@@ -529,6 +530,7 @@ struct scatterlist *sgl_alloc_order(unsigned long length, unsigned int order,
 		sg_set_page(sg, page, chunk_len, 0);
 		length -= chunk_len;
 		sg = sg_next(sg);
+		i++;
 	}
 	WARN_ONCE(length, "length = %ld\n", length);
 	return sgl;
-- 
2.14.1