From 8662e56c31cf23b61ca3d11b516efb94c35b8026 Mon Sep 17 00:00:00 2001 From: Lars-Peter Clausen Date: Wed, 15 Jul 2026 08:42:45 -0700 Subject: [PATCH] iio: buffer: Make IIO DMA fence release RCU-safe The `dma_fence` documentation states that if a custom release implementation is provided, the `dma_fence` object must be freed in an RCU-safe way. The current `iio_dma_fence` implementation uses `kfree()`, which might result in a use-after-free. Remove the custom `release` implementation. This makes the DMA fence core fall back to `dma_fence_free()`, which calls `kfree_rcu()` on the fence. This requires that the fence be the first member of `struct iio_dma_fence`. Using the default release method for extended DMA fence structures is a common pattern. Reported-by: codex:gpt-5.6 Fixes: 3e26d9f08fbe ("iio: core: Add new DMABUF interface infrastructure") Signed-off-by: Lars-Peter Clausen Cc: Signed-off-by: Jonathan Cameron --- drivers/iio/industrialio-buffer.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c index 31c06bffdce8..2c9ec93dff47 100644 --- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c @@ -54,6 +54,10 @@ struct iio_dmabuf_priv { }; struct iio_dma_fence { + /* + * Must remain the first member so the default release callback can pass + * the fence directly to dma_fence_free(). + */ struct dma_fence base; spinlock_t lock; /* protects base */ struct iio_dmabuf_priv *priv; @@ -1828,18 +1832,9 @@ iio_buffer_dma_fence_get_driver_name(struct dma_fence *fence) return "iio"; } -static void iio_buffer_dma_fence_release(struct dma_fence *fence) -{ - struct iio_dma_fence *iio_fence = - container_of(fence, struct iio_dma_fence, base); - - kfree(iio_fence); -} - static const struct dma_fence_ops iio_buffer_dma_fence_ops = { .get_driver_name = iio_buffer_dma_fence_get_driver_name, .get_timeline_name = iio_buffer_dma_fence_get_driver_name, - .release = iio_buffer_dma_fence_release, }; static int iio_buffer_enqueue_dmabuf(struct iio_dev_buffer_pair *ib,