1 files changed, 27 insertions, 16 deletions

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 8ce1f074c2d3..cc7398cc17d6 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -297,7 +297,7 @@ static const struct dma_buf_ops udmabuf_ops = {
 };
 
 #define SEALS_WANTED (F_SEAL_SHRINK)
-#define SEALS_DENIED (F_SEAL_WRITE)
+#define SEALS_DENIED (F_SEAL_WRITE|F_SEAL_FUTURE_WRITE)
 
 static int check_memfd_seals(struct file *memfd)
 {
@@ -317,12 +317,10 @@ static int check_memfd_seals(struct file *memfd)
 	return 0;
 }
 
-static int export_udmabuf(struct udmabuf *ubuf,
-			  struct miscdevice *device,
-			  u32 flags)
+static struct dma_buf *export_udmabuf(struct udmabuf *ubuf,
+				      struct miscdevice *device)
 {
 	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
-	struct dma_buf *buf;
 
 	ubuf->device = device;
 	exp_info.ops  = &udmabuf_ops;
@@ -330,11 +328,7 @@ static int export_udmabuf(struct udmabuf *ubuf,
 	exp_info.priv = ubuf;
 	exp_info.flags = O_RDWR;
 
-	buf = dma_buf_export(&exp_info);
-	if (IS_ERR(buf))
-		return PTR_ERR(buf);
-
-	return dma_buf_fd(buf, flags);
+	return dma_buf_export(&exp_info);
 }
 
 static long udmabuf_pin_folios(struct udmabuf *ubuf, struct file *memfd,
@@ -391,6 +385,7 @@ static long udmabuf_create(struct miscdevice *device,
 	struct folio **folios = NULL;
 	pgoff_t pgcnt = 0, pglimit;
 	struct udmabuf *ubuf;
+	struct dma_buf *dmabuf;
 	long ret = -EINVAL;
 	u32 i, flags;
 
@@ -436,23 +431,39 @@ static long udmabuf_create(struct miscdevice *device,
 			goto err;
 		}
 
+		/*
+		 * Take the inode lock to protect against concurrent
+		 * memfd_add_seals(), which takes this lock in write mode.
+		 */
+		inode_lock_shared(file_inode(memfd));
 		ret = check_memfd_seals(memfd);
-		if (ret < 0) {
-			fput(memfd);
-			goto err;
-		}
+		if (ret)
+			goto out_unlock;
 
 		ret = udmabuf_pin_folios(ubuf, memfd, list[i].offset,
 					 list[i].size, folios);
+out_unlock:
+		inode_unlock_shared(file_inode(memfd));
 		fput(memfd);
 		if (ret)
 			goto err;
 	}
 
 	flags = head->flags & UDMABUF_FLAGS_CLOEXEC ? O_CLOEXEC : 0;
-	ret = export_udmabuf(ubuf, device, flags);
-	if (ret < 0)
+	dmabuf = export_udmabuf(ubuf, device);
+	if (IS_ERR(dmabuf)) {
+		ret = PTR_ERR(dmabuf);
 		goto err;
+	}
+	/*
+	 * Ownership of ubuf is held by the dmabuf from here.
+	 * If the following dma_buf_fd() fails, dma_buf_put() cleans up both the
+	 * dmabuf and the ubuf (through udmabuf_ops.release).
+	 */
+
+	ret = dma_buf_fd(dmabuf, flags);
+	if (ret < 0)
+		dma_buf_put(dmabuf);
 
 	kvfree(folios);
 	return ret;