CVE-2022-48872: misc: fastrpc: Fix use-after-free race condition for maps

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

Description
===========

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

The Linux kernel CVE team has assigned CVE-2022-48872 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.1 with commit c68cfb718c8f and fixed in 5.4.230 with commit 556dfdb226ce
	Issue introduced in 5.1 with commit c68cfb718c8f and fixed in 5.10.165 with commit b171d0d2cf1b
	Issue introduced in 5.1 with commit c68cfb718c8f and fixed in 5.15.90 with commit 61a0890cb95a
	Issue introduced in 5.1 with commit c68cfb718c8f and fixed in 6.1.8 with commit 079c78c68714
	Issue introduced in 5.1 with commit c68cfb718c8f and fixed in 6.2 with commit 96b328d119ec

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-48872
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/misc/fastrpc.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/556dfdb226ce1e5231d8836159b23f8bb0395bf4
	https://git.kernel.org/stable/c/b171d0d2cf1b8387c72c8d325c5d5746fa271e39
	https://git.kernel.org/stable/c/61a0890cb95afec5c8a2f4a879de2b6220984ef1
	https://git.kernel.org/stable/c/079c78c68714f7d8d58e66c477b0243b31806907
	https://git.kernel.org/stable/c/96b328d119eca7563c1edcc4e1039a62e6370ecb