io_uring/ublk: report error when unregister operation fails

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>
Link: https://lore.kernel.org/r/20250228231432.642417-1-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 14 insertions, 4 deletions

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 3107a03d56b8..c9105030f0e3 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -973,26 +973,36 @@ unlock:
 }
 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);