Subject: [PATCH] udmabuf: fix DMA direction mismatch in release_udmabuf()

begin_cpu_udmabuf() maps the sg_table with the caller-provided direction (e.g., DMA_TO_DEVICE for a write-only sync), and caches it in ubuf->sg for reuse. However, release_udmabuf() always unmaps this sg_table with a hardcoded DMA_BIDIRECTIONAL, regardless of the direction that was originally used for the mapping.

With CONFIG_DMA_API_DEBUG=y this produces:

DMA-API: misc udmabuf: device driver frees DMA memory with different direction [device address=0x000000044a123000] [size=4096 bytes] [mapped with DMA_TO_DEVICE] [unmapped with DMA_BIDIRECTIONAL]

The issue was found during video playback when GStreamer performed a write-only DMA_BUF_IOCTL_SYNC on a udmabuf. It can be reproduced with CONFIG_DMA_API_DEBUG=y by creating a udmabuf from a memfd, performing a write-only sync (DMA_BUF_SYNC_WRITE without DMA_BUF_SYNC_READ), and closing the file descriptor.

Fix this by storing the DMA direction used when the sg_table is first created in begin_cpu_udmabuf(), and passing that same direction to put_sg_table() in release_udmabuf().

Fixes: 284562e1f348 ("udmabuf: implement begin_cpu_access/end_cpu_access hooks") Cc: stable@vger.kernel.org Signed-off-by: Mikhail Gavrilov mikhail.v.gavrilov@gmail.com

---

drivers/dma-buf/udmabuf.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index 94b8ecb892bb..d0836febefdd 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -40,6 +40,7 @@ struct udmabuf { struct folio **pinned_folios;

struct sg_table *sg;

• enum dma_data_direction sg_dir; struct miscdevice *device; pgoff_t *offsets;

}; @@ -235,7 +236,7 @@ static void release_udmabuf(struct dma_buf *buf) struct device *dev = ubuf->device->this_device;

if (ubuf->sg)

• put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL);
  

• put_sg_table(dev, ubuf->sg, ubuf->sg_dir);
  
  

  deinit_udmabuf(ubuf); kfree(ubuf);

@@ -253,6 +254,8 @@ static int begin_cpu_udmabuf(struct dma_buf *buf, if (IS_ERR(ubuf->sg)) { ret = PTR_ERR(ubuf->sg); ubuf->sg = NULL;

• } else {
  

• 	ubuf->sg_dir = direction;
  

Reviewed-by: Vivek Kasireddy vivek.kasireddy@intel.com

Thanks, Vivek

}

} else { dma_sync_sgtable_for_cpu(dev, ubuf->sg, direction); -- 2.53.0