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.