In the Linux kernel, the following vulnerability has been resolved: RDMA/core: Fix potential use after free in ib_free_cq() When accessing

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

RDMA/core: Fix potential use after free in ib_free_cq()

When accessing a CQ via the netlink path the only synchronization
mechanism for the said CQ is rdma_restrack_get().
Currently, rdma_restrack_del() is invoked at the end of
ib_free_cq(), which is too late, since by that point
vendor-specific resources associated with the CQ might already be
freed. This can leave a short window where the CQ remains accessible
through restrack, leading to a potential use-after-free.

Fix this by moving the rdma_restrack_del() call to be before the freeing
of the vendor-specific resources ensuring that the CQ is removed from
restrack before its internal resources are released.
This guarantees that no new users hold references to a CQ that is in
the process of destruction.