CVE-2023-52707

In the Linux kernel, the following vulnerability has been resolved:
sched/psi: Fix use-after-free in ep_remove_wait_queue() If a non-root
cgroup gets removed when there is a thread that registered trigger and is
polling on a pressure file within the cgroup, the polling waitqueue gets
freed in the following path: do_rmdir cgroup_rmdir kernfs_drain_open_files
cgroup_file_release cgroup_pressure_release psi_trigger_destroy However,
the polling thread still has a reference to the pressure file and will
access the freed waitqueue when the file is closed or upon exit: fput
ep_eventpoll_release ep_free ep_remove_wait_queue remove_wait_queue This
results in use-after-free as pasted below. The fundamental problem here is
that cgroup_file_release() (and consequently waitqueue’s lifetime) is not
tied to the file’s real lifetime. Using wake_up_pollfree() here might be
less than ideal, but it is in line with the comment at commit 42288cb44c4b
(“wait: add wake_up_pollfree()”) since the waitqueue’s lifetime is not tied
to file’s one and can be considered as another special case. While this
would be fixable by somehow making cgroup_file_release() be tied to the
fput(), it would require sizable refactoring at cgroups or higher layer
which might be more justifiable if we identify more cases like this. BUG:
KASAN: use-after-free in _raw_spin_lock_irqsave+0x60/0xc0 Write of size 4
at addr ffff88810e625328 by task a.out/4404 CPU: 19 PID: 4404 Comm: a.out
Not tainted 6.2.0-rc6 #38 Hardware name: Amazon EC2 c5a.8xlarge/, BIOS 1.0
10/16/2017 Call Trace: <TASK> dump_stack_lvl+0x73/0xa0
print_report+0x16c/0x4e0 kasan_report+0xc3/0xf0
kasan_check_range+0x2d2/0x310 _raw_spin_lock_irqsave+0x60/0xc0
remove_wait_queue+0x1a/0xa0 ep_free+0x12c/0x170
ep_eventpoll_release+0x26/0x30 __fput+0x202/0x400 task_work_run+0x11d/0x170
do_exit+0x495/0x1130 do_group_exit+0x100/0x100 get_signal+0xd67/0xde0
arch_do_signal_or_restart+0x2a/0x2b0 exit_to_user_mode_prepare+0x94/0x100
syscall_exit_to_user_mode+0x20/0x40 do_syscall_64+0x52/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd </TASK> Allocated by task 4404:
kasan_set_track+0x3d/0x60 __kasan_kmalloc+0x85/0x90
psi_trigger_create+0x113/0x3e0 pressure_write+0x146/0x2e0
cgroup_file_write+0x11c/0x250 kernfs_fop_write_iter+0x186/0x220
vfs_write+0x3d8/0x5c0 ksys_write+0x90/0x110 do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd Freed by task 4407:
kasan_set_track+0x3d/0x60 kasan_save_free_info+0x27/0x40
____kasan_slab_free+0x11d/0x170 slab_free_freelist_hook+0x87/0x150
__kmem_cache_free+0xcb/0x180 psi_trigger_destroy+0x2e8/0x310
cgroup_file_release+0x4f/0xb0 kernfs_drain_open_files+0x165/0x1f0
kernfs_drain+0x162/0x1a0 __kernfs_remove+0x1fb/0x310
kernfs_remove_by_name_ns+0x95/0xe0 cgroup_addrm_files+0x67f/0x700
cgroup_destroy_locked+0x283/0x3c0 cgroup_rmdir+0x29/0x100
kernfs_iop_rmdir+0xd1/0x140 vfs_rmdir+0xfe/0x240 do_rmdir+0x13d/0x280
__x64_sys_rmdir+0x2c/0x30 do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd