[PATCH 4/5] dma-pool: release CMA pages on atomic_pool_expand() error path

[Marek Szyprowski]

atomic_pool_expand() may allocate the pool backing pages from CMA via
dma_alloc_from_contiguous(), but the error path unconditionally frees
them with __free_pages(). This hands CMA pages to the buddy allocator
while leaving them marked as allocated in the CMA bitmap, permanently
leaking CMA capacity on every failed expansion.

Try dma_release_from_contiguous() first and fall back to __free_pages()
only for pages that did not come from CMA, as the code did before CMA
allocation was temporarily removed from the pool.

Fixes: d7e673ec2c8e ("dma-pool: Only allocate from CMA when in same memory zone")
Closes: https://sashiko.dev/#/bug/linux-fdfc6e83-15e4-4980-9818-691b034397e7
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
 kernel/dma/pool.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 00f422a1e896..381b3cb28368 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -152,7 +152,8 @@ static int atomic_pool_expand(struct dma_gen_pool *dma_pool, size_t pool_size,
 	dma_common_free_remap(addr, pool_size);
 free_page:
 #endif
-	if (!leak_pages)
+	if (!leak_pages &&
+	    !dma_release_from_contiguous(NULL, page, 1 << order))
 		__free_pages(page, order);
 out:
 	return ret;
-- 
2.43.0