From: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Date: Sat, 14 Mar 2026 23:27:22 +0000 (+0500)
Subject: udmabuf: fix DMA direction mismatch in release_udmabuf()
X-Git-Tag: v7.2-rc1~141^2~26^2~186
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=fb7b1a0ab25a6077d26cb3829e31743972d4f31d;p=thirdparty%2Flinux.git

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>
Reviewed-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Link: https://patch.msgid.link/20260314232722.15555-1-mikhail.v.gavrilov@gmail.com
---

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 5d68786044513..94b26ea706a3f 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;
 };
 
@@ -212,7 +213,7 @@ 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);
@@ -230,6 +231,8 @@ 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);