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

rxrpc: Fix listen() setting the bar too high for the prealloc rings

AF_RXRPC's listen() handler lets you set the backlog up to 32 (if you bump
up the sysctl), but whilst the preallocation circular buffers have 32 slots
in them, one of them has to be a dead slot because we're using CIRC_CNT().

This means that listen(rxrpc_sock, 32) will cause an oops when the socket
is closed because rxrpc_service_prealloc_one() allocated one too many calls
and rxrpc_discard_prealloc() won't then be able to get rid of them because
it'll think the ring is empty.  rxrpc_release_calls_on_socket() then tries
to abort them, but oopses because call->peer isn't yet set.

Fix this by setting the maximum backlog to RXRPC_BACKLOG_MAX - 1 to match
the ring capacity.

 BUG: kernel NULL pointer dereference, address: 0000000000000086
 ...
 RIP: 0010:rxrpc_send_abort_packet+0x73/0x240 [rxrpc]
 Call Trace:
  <TASK>
  ? __wake_up_common_lock+0x7a/0x90
  ? rxrpc_notify_socket+0x8e/0x140 [rxrpc]
  ? rxrpc_abort_call+0x4c/0x60 [rxrpc]
  rxrpc_release_calls_on_socket+0x107/0x1a0 [rxrpc]
  rxrpc_release+0xc9/0x1c0 [rxrpc]
  __sock_release+0x37/0xa0
  sock_close+0x11/0x20
  __fput+0x89/0x240
  task_work_run+0x59/0x90
  do_exit+0x319/0xaa0

https://git.kernel.org/stable/c/369de57492c4f1a42563c5a3bd365822ca3bfc79

https://git.kernel.org/stable/c/4a3a78b7918bdd723d8c7c9786522ca969bffcc4

https://git.kernel.org/stable/c/5b4826657d36c218e9f08e8d3223b0edce3de88f

https://git.kernel.org/stable/c/616f76498d5ddf26b997caf64a95cda3c8a55533

https://git.kernel.org/stable/c/61fb38cfbb1d54d3dafd0c25752f684b3cd00b32

https://git.kernel.org/stable/c/88e22159750b0d55793302eeed8ee603f5c1a95c

https://git.kernel.org/stable/c/91b34bf0409f43bb60453bab23c5beadd726d022

https://git.kernel.org/stable/c/b3a9b227d5e7467b8518160ff034ea22bb9de573

https://git.kernel.org/stable/c/e198f1930050e3115c80b67d9249f80f98a27c67