Add a new dma-buf ioctl() op, DMA_BUF_IOCTL_REVOKE, connected to a new (optional) dma_buf_ops callback, revoke(). An exporter receiving this will _permanently_ revoke the DMABUF, meaning it can no longer be mapped/attached/mmap()ed. It also guarantees that existing importers have been detached (e.g. via move_notify) and all mappings made inaccessible.
This is useful for lifecycle management in scenarios where a process has created a DMABUF representing a resource, then delegated it to a client process; access to the resource is revoked when the client is deemed "done", and the resource can be safely re-used elsewhere.
Signed-off-by: Matt Evans mattev@meta.com --- drivers/dma-buf/dma-buf.c | 5 +++++ include/linux/dma-buf.h | 22 ++++++++++++++++++++++ include/uapi/linux/dma-buf.h | 1 + 3 files changed, 28 insertions(+)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index edaa9e4ee4ae..b9b315317f2d 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -561,6 +561,11 @@ static long dma_buf_ioctl(struct file *file, case DMA_BUF_IOCTL_IMPORT_SYNC_FILE: return dma_buf_import_sync_file(dmabuf, (const void __user *)arg); #endif + case DMA_BUF_IOCTL_REVOKE: + if (dmabuf->ops->revoke) + return dmabuf->ops->revoke(dmabuf); + else + return -EINVAL;
default: return -ENOTTY; diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 0bc492090237..a68c9ad7aebd 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -277,6 +277,28 @@ struct dma_buf_ops {
int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map); void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map); + + /** + * @revoke: + * + * This callback is invoked from a userspace + * DMA_BUF_IOCTL_REVOKE operation, and requests that access to + * the buffer is immediately and permanently revoked. On + * successful return, the buffer is not accessible through any + * mmap() or dma-buf import. The request fails if the buffer + * is pinned; otherwise, the exporter marks the buffer as + * inaccessible and uses the move_notify callback to inform + * importers of the change. The buffer is permanently + * disabled, and the exporter must refuse all map, mmap, + * attach, etc. requests. + * + * Returns: + * + * 0 on success, or a negative error code on failure: + * -ENODEV if the associated device no longer exists/is closed. + * -EBADFD if the buffer has already been revoked. + */ + int (*revoke)(struct dma_buf *dmabuf); };
/** diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h index 5a6fda66d9ad..84bf2dd2d0f3 100644 --- a/include/uapi/linux/dma-buf.h +++ b/include/uapi/linux/dma-buf.h @@ -178,5 +178,6 @@ struct dma_buf_import_sync_file { #define DMA_BUF_SET_NAME_B _IOW(DMA_BUF_BASE, 1, __u64) #define DMA_BUF_IOCTL_EXPORT_SYNC_FILE _IOWR(DMA_BUF_BASE, 2, struct dma_buf_export_sync_file) #define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW(DMA_BUF_BASE, 3, struct dma_buf_import_sync_file) +#define DMA_BUF_IOCTL_REVOKE _IO(DMA_BUF_BASE, 4)
#endif