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

misc: fastrpc: Fix use-after-free race condition for maps

It is possible that in between calling fastrpc_map_get() until
map->fl->lock is taken in fastrpc_free_map(), another thread can call
fastrpc_map_lookup() and get a reference to a map that is about to be
deleted.

Rewrite fastrpc_map_get() to only increase the reference count of a map
if it's non-zero. Propagate this to callers so they can know if a map is
about to be deleted.

Fixes this warning:
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 5 PID: 10100 at lib/refcount.c:25 refcount_warn_saturate
...
Call trace:
 refcount_warn_saturate
 [fastrpc_map_get inlined]
 [fastrpc_map_lookup inlined]
 fastrpc_map_create
 fastrpc_internal_invoke
 fastrpc_device_ioctl
 __arm64_sys_ioctl
 invoke_syscall

kernel.org https://git.kernel.org/stable/c/079c78c68714f7d8d58e66c477b0243b31806907 [No types assigned]

kernel.org https://git.kernel.org/stable/c/556dfdb226ce1e5231d8836159b23f8bb0395bf4 [No types assigned]

kernel.org https://git.kernel.org/stable/c/61a0890cb95afec5c8a2f4a879de2b6220984ef1 [No types assigned]

kernel.org https://git.kernel.org/stable/c/96b328d119eca7563c1edcc4e1039a62e6370ecb [No types assigned]

kernel.org https://git.kernel.org/stable/c/b171d0d2cf1b8387c72c8d325c5d5746fa271e39 [No types assigned]