CVE-2023-52447

In the Linux kernel, the following vulnerability has been resolved: bpf:
Defer the free of inner map when necessary When updating or deleting an
inner map in map array or map htab, the map may still be accessed by
non-sleepable program or sleepable program. However bpf_map_fd_put_ptr()
decreases the ref-counter of the inner map directly through bpf_map_put(),
if the ref-counter is the last one (which is true for most cases), the
inner map will be freed by ops->map_free() in a kworker. But for now, most
.map_free() callbacks don’t use synchronize_rcu() or its variants to wait
for the elapse of a RCU grace period, so after the invocation of
ops->map_free completes, the bpf program which is accessing the inner map
may incur use-after-free problem. Fix the free of inner map by invoking
bpf_map_free_deferred() after both one RCU grace period and one tasks trace
RCU grace period if the inner map has been removed from the outer map
before. The deferment is accomplished by using call_rcu() or
call_rcu_tasks_trace() when releasing the last ref-counter of bpf map. The
newly-added rcu_head field in bpf_map shares the same storage space with
work field to reduce the size of bpf_map.

Notes