Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

RDMA/uverbs: Guard legacy bundles without method_elm

The legacy write() path dispatches through a uverbs_api_write_method, but the uverbs_attr_bundle passed to provider code does not have an ioctl method element. If malformed provider input causes the common uverbs validation code to emit an error message, uverbs_get_handler_fn() dereferences the uninitialized method_elm pointer.

Initialize method_elm explicitly for legacy bundles and make uverbs_get_handler_fn() return NULL when no ioctl method is present. The legacy dispatcher continues to use its local write method, while the ioctl path continues to use the registered ioctl handler.