CVE-2022-50135: NULL Pointer Dereference

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

RDMA/rxe: Fix BUG: KASAN: null-ptr-deref in rxe_qp_do_cleanup

The function rxe_create_qp calls rxe_qp_from_init. If some error occurs, the error handler of function rxe_qp_from_init will set both scq and rcq to NULL.

Then rxe_create_qp calls rxe_put to handle qp. In the end, rxe_qp_do_cleanup is called by rxe_put. rxe_qp_do_cleanup directly accesses scq and rcq before checking them. This will cause null-ptr-deref error.

The call graph is as below:

rxe_create_qp { ... rxe_qp_from_init { ... err1: ... qp->rcq = NULL; <---rcq is set to NULL qp->scq = NULL; <---scq is set to NULL ... }

qp_init: rxe_put{ ... rxe_qp_do_cleanup { ... atomic_dec(&qp->scq->num_wq); <--- scq is accessed ... atomic_dec(&qp->rcq->num_wq); <--- rcq is accessed } }