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@acm.org>
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 5d63a88..c448642 100644 (file)
--- 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;
                }