linux-kernel - [PATCH AUTOSEL 5.4 79/80] sgl_alloc

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Message-Id: <20201026235516.1025100-79-sashal@kernel.org>
Date:   Mon, 26 Oct 2020 19:55:15 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Douglas Gilbert <dgilbert@...erlog.com>,
        Bart Van Assche <bvanassche@....org>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.4 79/80] sgl_alloc_order: fix memory leak

From: Douglas Gilbert <dgilbert@...erlog.com>

[ Upstream commit b2a182a40278bc5849730e66bca01a762188ed86 ]

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>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 lib/scatterlist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 5813072bc5895..29346184fcf2e 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