[SRU][J][PATCH 0/2] CVE-2023-52447

[Bethany Jamison]

[Impact]

 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.

[Fix]

Mantic: pending
Jammy:  Prereq commit and fix commit (linux-5.15.y) cherry-picked cleanly.
Focal:  not-affected
Bionic: not-affected
Xenial: not-affected
Trusty: not-affected

[Test Case]

Compile and boot tested.

[Where problems could occur]

This fix affects those who use the Berkeley Packet Filter (bpf), an issue
with this fix would be visable with unpredicted system behavior or even
a system crash.

Hou Tao (1):
  bpf: Defer the free of inner map when necessary

Paul E. McKenney (1):
  rcu-tasks: Provide rcu_trace_implies_rcu_gp()

 include/linux/bpf.h      |  7 ++++++-
 include/linux/rcupdate.h | 12 ++++++++++++
 kernel/bpf/map_in_map.c  | 11 ++++++++---
 kernel/bpf/syscall.c     | 26 ++++++++++++++++++++++++--
 kernel/rcu/tasks.h       |  2 ++
 5 files changed, 52 insertions(+), 6 deletions(-)

-- 
2.34.1