[PATCH] io_uring/ublk: report error when unregister operation fails

[Caleb Sander Mateos <csander@purestorage.com>]

Indicate to userspace applications if a UBLK_IO_UNREGISTER_IO_BUF
command specifies an invalid buffer index by returning an error code.
Return -EINVAL if no buffer is registered with the given index, and
-EBUSY if the registered buffer is not a kernel bvec.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 drivers/block/ublk_drv.c     |  3 +--
 include/linux/io_uring/cmd.h |  4 ++--
 io_uring/rsrc.c              | 18 ++++++++++++++----
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index b5cf92baaf0f..512cbd456817 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1785,12 +1785,11 @@ static int ublk_register_io_buf(struct io_uring_cmd *cmd,
 
 static int ublk_unregister_io_buf(struct io_uring_cmd *cmd,
 				  const struct ublksrv_io_cmd *ub_cmd,
 				  unsigned int issue_flags)
 {
-	io_buffer_unregister_bvec(cmd, ub_cmd->addr, issue_flags);
-	return 0;
+	return io_buffer_unregister_bvec(cmd, ub_cmd->addr, issue_flags);
 }
 
 static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 			       unsigned int issue_flags,
 			       const struct ublksrv_io_cmd *ub_cmd)
diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index cf8d80d84734..05d7b6145731 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -127,9 +127,9 @@ static inline struct io_uring_cmd_data *io_uring_cmd_get_async_data(struct io_ur
 }
 
 int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct request *rq,
 			    void (*release)(void *), unsigned int index,
 			    unsigned int issue_flags);
-void io_buffer_unregister_bvec(struct io_uring_cmd *cmd, unsigned int index,
-			       unsigned int issue_flags);
+int io_buffer_unregister_bvec(struct io_uring_cmd *cmd, unsigned int index,
+			      unsigned int issue_flags);
 
 #endif /* _LINUX_IO_URING_CMD_H */
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 45bfb37bca1e..29c0c31092eb 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -975,30 +975,40 @@ int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct request *rq,
 	io_ring_submit_unlock(ctx, issue_flags);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(io_buffer_register_bvec);
 
-void io_buffer_unregister_bvec(struct io_uring_cmd *cmd, unsigned int index,
-			       unsigned int issue_flags)
+int io_buffer_unregister_bvec(struct io_uring_cmd *cmd, unsigned int index,
+			      unsigned int issue_flags)
 {
 	struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
 	struct io_rsrc_data *data = &ctx->buf_table;
 	struct io_rsrc_node *node;
+	int ret = 0;
 
 	io_ring_submit_lock(ctx, issue_flags);
-	if (index >= data->nr)
+	if (index >= data->nr) {
+		ret = -EINVAL;
 		goto unlock;
+	}
 	index = array_index_nospec(index, data->nr);
 
 	node = data->nodes[index];
-	if (!node || !node->buf->is_kbuf)
+	if (!node) {
+		ret = -EINVAL;
 		goto unlock;
+	}
+	if (!node->buf->is_kbuf) {
+		ret = -EBUSY;
+		goto unlock;
+	}
 
 	io_put_rsrc_node(ctx, node);
 	data->nodes[index] = NULL;
 unlock:
 	io_ring_submit_unlock(ctx, issue_flags);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(io_buffer_unregister_bvec);
 
 static int io_import_fixed(int ddir, struct iov_iter *iter,
 			   struct io_mapped_ubuf *imu,
-- 
2.45.2