From f3df4a783bce399fb2641e2cd6f3ea74151be975 Mon Sep 17 00:00:00 2001 From: Mikhail Gavrilov Date: Sun, 15 Mar 2026 04:27:22 +0500 Subject: [PATCH] udmabuf: fix DMA direction mismatch in release_udmabuf() commit fb7b1a0ab25a6077d26cb3829e31743972d4f31d upstream. 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 Reviewed-by: Vivek Kasireddy Signed-off-by: Vivek Kasireddy Link: https://patch.msgid.link/20260314232722.15555-1-mikhail.v.gavrilov@gmail.com Signed-off-by: Greg Kroah-Hartman --- 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 97e0ea90e7de..75cbcc5672e6 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -25,6 +25,7 @@ struct udmabuf { pgoff_t pagecount; struct page **pages; struct sg_table *sg; + enum dma_data_direction sg_dir; struct miscdevice *device; }; @@ -111,7 +112,7 @@ static void release_udmabuf(struct dma_buf *buf) pgoff_t pg; if (ubuf->sg) - put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL); + put_sg_table(dev, ubuf->sg, ubuf->sg_dir); for (pg = 0; pg < ubuf->pagecount; pg++) put_page(ubuf->pages[pg]); @@ -131,6 +132,8 @@ 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; } } else { dma_sync_sgtable_for_cpu(dev, ubuf->sg, direction);