CVE-2021-47261

In the Linux kernel, the following vulnerability has been resolved: IB/mlx5: Fix initializing CQ fragments buffer The function init_cq_frag_buf() can be called to initialize the current CQ fragments buffer cq->buf, or the temporary cq->resize_buf that is filled during CQ resize operation. However, the offending commit started to use function get_cqe() for getting the CQEs, the issue with this change is that get_cqe() always returns CQEs from cq->buf, which leads us to initialize the wrong buffer, and in case of enlarging the CQ we try to access elements beyond the size of the current cq->buf and eventually hit a kernel panic. [exception RIP: init_cq_frag_buf+103] [ffff9f799ddcbcd8] mlx5_ib_resize_cq at ffffffffc0835d60 [mlx5_ib] [ffff9f799ddcbdb0] ib_resize_cq at ffffffffc05270df [ib_core] [ffff9f799ddcbdc0] llt_rdma_setup_qp at ffffffffc0a6a712 [llt] [ffff9f799ddcbe10] llt_rdma_cc_event_action at ffffffffc0a6b411 [llt] [ffff9f799ddcbe98] llt_rdma_client_conn_thread at ffffffffc0a6bb75 [llt] [ffff9f799ddcbec8] kthread at ffffffffa66c5da1 [ffff9f799ddcbf50] ret_from_fork_nospec_begin at ffffffffa6d95ddd Fix it by getting the needed CQE by calling mlx5_frag_buf_get_wqe() that takes the correct source buffer as a parameter.

In the Linux kernel, the following vulnerability has been resolved: IB/mlx5: Fix initializing CQ fragments buffer The function init_cq_frag_buf() can be called to initialize the current CQ fragments buffer cq->buf, or the temporary cq->resize_buf that is filled during CQ resize operation. However, the offending commit started to use function get_cqe() for getting the CQEs, the issue with this change is that get_cqe() always returns CQEs from cq->buf, which leads us to initialize the wrong buffer, and in case of enlarging the CQ we try to access elements beyond the size of the current cq->buf and eventually hit a kernel panic. [exception RIP: init_cq_frag_buf+103] [ffff9f799ddcbcd8] mlx5_ib_resize_cq at ffffffffc0835d60 [mlx5_ib] [ffff9f799ddcbdb0] ib_resize_cq at ffffffffc05270df [ib_core] [ffff9f799ddcbdc0] llt_rdma_setup_qp at ffffffffc0a6a712 [llt] [ffff9f799ddcbe10] llt_rdma_cc_event_action at ffffffffc0a6b411 [llt] [ffff9f799ddcbe98] llt_rdma_client_conn_thread at ffffffffc0a6bb75 [llt] [ffff9f799ddcbec8] kthread at ffffffffa66c5da1 [ffff9f799ddcbf50] ret_from_fork_nospec_begin at ffffffffa6d95ddd Fix it by getting the needed CQE by calling mlx5_frag_buf_get_wqe() that takes the correct source buffer as a parameter.

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: IB/mlx5: Corrección al inicializar el búfer de fragmentos CQ. Se puede llamar a la función init_cq_frag_buf() para inicializar el búfer de fragmentos CQ actual cq->buf, o el cq->resize_buf temporal que es rellenado durante la operación de cambio de tamaño de CQ. Sin embargo, la confirmación infractora comenzó a usar la función get_cqe() para obtener los CQE, el problema con este cambio es que get_cqe() siempre devuelve CQE desde cq->buf, lo que nos lleva a inicializar el búfer incorrecto y, en caso de ampliarlo, En el CQ intentamos acceder a elementos más allá del tamaño del cq->buf actual y finalmente entramos en pánico en el kernel. [excepción RIP: init_cq_frag_buf+103] [ffff9f799ddcbcd8] mlx5_ib_resize_cq en fffffffc0835d60 [mlx5_ib] [ffff9f799ddcbdb0] ib_resize_cq en fffffffc05270df [ib_core] [ffff9f799ddcbdc0] _rdma_setup_qp en ffffffffc0a6a712 [llt] [ffff9f799ddcbe10] llt_rdma_cc_event_action en ffffffffc0a6b411 [llt] [ffff9f799ddcbe98] llt_rdma_client_conn_thread en ffffffffc0a6bb75 [llt] [ffff9f799ddcbec8] kthread en ffffffffa66c5da1 [ffff9f799ddcbf50] ret_from_fork_nospec_begin en ffffffffa6d95ddd Arréglelo obteniendo el CQE necesario llamando a mlx5_frag_buf_get_wqe() que toma el búfer de origen correcto como parámetro.