linux-kernel - [RESEND PATCH] sgl_alloc

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Message-Id: <20201015185735.5480-1-dgilbert@interlog.com>
Date:   Thu, 15 Oct 2020 14:57:35 -0400
From:   Douglas Gilbert <dgilbert@...erlog.com>
To:     linux-scsi@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     martin.petersen@...cle.com, axboe@...nel.dk, bvanassche@....org
Subject: [RESEND PATCH] sgl_alloc_order: fix memory leak

sgl_alloc_order() can fail when 'length' is large on a memory
constrained system. When order > 0 it will potentially be
making several multi-page allocations with the later ones more
likely to fail than the earlier one. So it is important that
sgl_alloc_order() frees up any pages it has obtained before
returning NULL. In the case when order > 0 it calls the wrong
free page function and leaks. In testing the leak was
sufficient to bring down my 8 GiB laptop with OOM.

Reviewed-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: Douglas Gilbert <dgilbert@...erlog.com>
---
 lib/scatterlist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 5d63a8857f36..c448642e0f78 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -514,7 +514,7 @@ struct scatterlist *sgl_alloc_order(unsigned long long length,
 		elem_len = min_t(u64, length, PAGE_SIZE << order);
 		page = alloc_pages(gfp, order);
 		if (!page) {
-			sgl_free(sgl);
+			sgl_free_order(sgl, order);
 			return NULL;
 		}

-- 
2.25.1