CVE-2022-49939

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

binder: fix UAF of ref->proc caused by race condition

A transaction of type BINDER_TYPE_WEAK_HANDLE can fail to increment the

reference for a node. In this case, the target proc normally releases

the failed reference upon close as expected. However, if the target is

dying in parallel the call will race with binder_deferred_release(), so

the target could have released all of its references by now leaving the

cleanup of the new failed reference unhandled.

The transaction then ends and the target proc gets released making the

ref->proc now a dangling pointer. Later on, ref->node is closed and we

attempt to take spin_lock(&ref->proc->inner_lock), which leads to the

use-after-free bug reported below. Let's fix this by cleaning up the

failed reference on the spot instead of relying on the target to do so.

==================================================================

BUG: KASAN: use-after-free in _raw_spin_lock+0xa8/0x150

Write of size 4 at addr ffff5ca207094238 by task kworker/1:0/590

CPU: 1 PID: 590 Comm: kworker/1:0 Not tainted 5.19.0-rc8 #10

Hardware name: linux,dummy-virt (DT)

Workqueue: events binder_deferred_func

Call trace:

dump_backtrace.part.0+0x1d0/0x1e0

show_stack+0x18/0x70

dump_stack_lvl+0x68/0x84

print_report+0x2e4/0x61c

kasan_report+0xa4/0x110

kasan_check_range+0xfc/0x1a4

__kasan_check_write+0x3c/0x50

_raw_spin_lock+0xa8/0x150

binder_deferred_func+0x5e0/0x9b0

process_one_work+0x38c/0x5f0

worker_thread+0x9c/0x694

kthread+0x188/0x190

ret_from_fork+0x10/0x20