From f25ec4627d935dedfb5fe83bd2c2678cdcc19611 Mon Sep 17 00:00:00 2001 From: Lars-Peter Clausen Date: Wed, 15 Jul 2026 08:42:44 -0700 Subject: [PATCH] iio: buffer: Tie IIO dma fence lock lifetime to the fence The `iio_dma_fence` implementation currently uses a lock embedded in the `iio_dmabuf_priv`. But the `iio_dma_fence` can outlive the `iio_dmabuf_priv`, which can cause a use-after-free. Tie the lifetime of the lock to the lifetime of the fence by embedding them in the same struct. We can't just hold a reference to the `iio_dmabuf_priv` from the `iio_dma_fence` since `iio_buffer_dmabuf_release()` might sleep and the fence release callback is not allowed to sleep. Note that the `dma_fence` framework now has an internal lock that gets used when the passing `NULL` for `lock` in `dma_fence_init()`, but in order to allow this patch to be backportable use an external lock. 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 | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c index 04b3916f89e2..31c06bffdce8 100644 --- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c @@ -47,9 +47,6 @@ struct iio_dmabuf_priv { u64 context; - /* Spinlock used for locking the dma_fence */ - spinlock_t lock; - struct dma_buf_attachment *attach; struct sg_table *sgt; enum dma_data_direction dir; @@ -58,6 +55,7 @@ struct iio_dmabuf_priv { struct iio_dma_fence { struct dma_fence base; + spinlock_t lock; /* protects base */ struct iio_dmabuf_priv *priv; struct work_struct work; }; @@ -1706,7 +1704,6 @@ static int iio_buffer_attach_dmabuf(struct iio_dev_buffer_pair *ib, if (!priv) return -ENOMEM; - spin_lock_init(&priv->lock); priv->context = dma_fence_context_alloc(1); dmabuf = dma_buf_get(fd); @@ -1896,6 +1893,8 @@ static int iio_buffer_enqueue_dmabuf(struct iio_dev_buffer_pair *ib, goto err_attachment_put; } + spin_lock_init(&fence->lock); + fence->priv = priv; seqno = atomic_add_return(1, &priv->seqno); @@ -1906,7 +1905,7 @@ static int iio_buffer_enqueue_dmabuf(struct iio_dev_buffer_pair *ib, * the dma_fence. */ dma_fence_init(&fence->base, &iio_buffer_dma_fence_ops, - &priv->lock, priv->context, seqno); + &fence->lock, priv->context, seqno); ret = iio_dma_resv_lock(dmabuf, nonblock); if (ret)