[RESEND PATCH] sgl_alloc_order: fix memory leak

[RESEND PATCH] sgl_alloc_order: fix memory leak

[Douglas Gilbert]

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@acm.org>
Signed-off-by: Douglas Gilbert <dgilbert@interlog.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

Re: [RESEND PATCH] sgl_alloc_order: fix memory leak

[Jens Axboe]

On 10/15/20 12:57 PM, Douglas Gilbert wrote:
> 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.

I've picked this one up, thanks.

-- 
Jens Axboe