CVE-2025-38176

Published Jul 4, 2025

Last updated 3 months ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: binder: fix use-after-free in binderfs_evict_inode() Running 'stress-ng --binderfs 16 --timeout 300' under KASAN-enabled kernel, I've noticed the following: BUG: KASAN: slab-use-after-free in binderfs_evict_inode+0x1de/0x2d0 Write of size 8 at addr ffff88807379bc08 by task stress-ng-binde/1699 CPU: 0 UID: 0 PID: 1699 Comm: stress-ng-binde Not tainted 6.14.0-rc7-g586de92313fc-dirty #13 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x1c2/0x2a0 ? __pfx_dump_stack_lvl+0x10/0x10 ? __pfx__printk+0x10/0x10 ? __pfx_lock_release+0x10/0x10 ? __virt_addr_valid+0x18c/0x540 ? __virt_addr_valid+0x469/0x540 print_report+0x155/0x840 ? __virt_addr_valid+0x18c/0x540 ? __virt_addr_valid+0x469/0x540 ? __phys_addr+0xba/0x170 ? binderfs_evict_inode+0x1de/0x2d0 kasan_report+0x147/0x180 ? binderfs_evict_inode+0x1de/0x2d0 binderfs_evict_inode+0x1de/0x2d0 ? __pfx_binderfs_evict_inode+0x10/0x10 evict+0x524/0x9f0 ? __pfx_lock_release+0x10/0x10 ? __pfx_evict+0x10/0x10 ? do_raw_spin_unlock+0x4d/0x210 ? _raw_spin_unlock+0x28/0x50 ? iput+0x697/0x9b0 __dentry_kill+0x209/0x660 ? shrink_kill+0x8d/0x2c0 shrink_kill+0xa9/0x2c0 shrink_dentry_list+0x2e0/0x5e0 shrink_dcache_parent+0xa2/0x2c0 ? __pfx_shrink_dcache_parent+0x10/0x10 ? __pfx_lock_release+0x10/0x10 ? __pfx_do_raw_spin_lock+0x10/0x10 do_one_tree+0x23/0xe0 shrink_dcache_for_umount+0xa0/0x170 generic_shutdown_super+0x67/0x390 kill_litter_super+0x76/0xb0 binderfs_kill_super+0x44/0x90 deactivate_locked_super+0xb9/0x130 cleanup_mnt+0x422/0x4c0 ? lockdep_hardirqs_on+0x9d/0x150 task_work_run+0x1d2/0x260 ? __pfx_task_work_run+0x10/0x10 resume_user_mode_work+0x52/0x60 syscall_exit_to_user_mode+0x9a/0x120 do_syscall_64+0x103/0x210 ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0xcac57b Code: c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e fa 31 f6 e9 05 00 00 00 0f 1f 44 00 00 f3 0f 1e fa b8 RSP: 002b:00007ffecf4226a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 RAX: 0000000000000000 RBX: 00007ffecf422720 RCX: 0000000000cac57b RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffecf422850 RBP: 00007ffecf422850 R08: 0000000028d06ab1 R09: 7fffffffffffffff R10: 3fffffffffffffff R11: 0000000000000246 R12: 00007ffecf422718 R13: 00007ffecf422710 R14: 00007f478f87b658 R15: 00007ffecf422830 </TASK> Allocated by task 1705: kasan_save_track+0x3e/0x80 __kasan_kmalloc+0x8f/0xa0 __kmalloc_cache_noprof+0x213/0x3e0 binderfs_binder_device_create+0x183/0xa80 binder_ctl_ioctl+0x138/0x190 __x64_sys_ioctl+0x120/0x1b0 do_syscall_64+0xf6/0x210 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 1705: kasan_save_track+0x3e/0x80 kasan_save_free_info+0x46/0x50 __kasan_slab_free+0x62/0x70 kfree+0x194/0x440 evict+0x524/0x9f0 do_unlinkat+0x390/0x5b0 __x64_sys_unlink+0x47/0x50 do_syscall_64+0xf6/0x210 entry_SYSCALL_64_after_hwframe+0x77/0x7f This 'stress-ng' workload causes the concurrent deletions from 'binder_devices' and so requires full-featured synchronization to prevent list corruption. I've found this issue independently but pretty sure that syzbot did the same, so Reported-by: and Closes: should be applicable here as well.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Modified
Products
linux_kernel

Risk scores

CVSS 3.1

Type
Primary
Base score
7.8
Impact score
5.9
Exploitability score
1.8
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity
HIGH

Weaknesses

nvd@nist.gov
CWE-416

Social media

Hype score
Not currently trending

Configurations

  1. In the Linux kernel, the following vulnerability has been resolved: cgroup: Avoid iteration of dying tasks with zero refcount The commit 260fbcb92bbea ("cgroup: Move dying_tasks cleanup from cgroup_task_release() to cgroup_task_free()") extended the lifetime of tasks on the dying_tasks list. The iterators have provision to go through dying_tasks because of dying threadgroup leaders or explicit CSS_TASK_ITER_WITH_DEAD, however, it was expected that such tasks can obtain a new reference (that is possible before cgroup_task_release()/put_task_struct_rcu_user()). The tasks after cgroup_task_release() and before cgroup_task_free() are subject to race when they may or may not have ->usage count > 0. The race window is between css_task_iter_next() invocations when css_set_lock is released and we may arrive at a new ->task_pos. The iterator should not attempt to resurrect tasks whose ->usage count dropped to zero. (When that happens, __put_task_struct_rcu_cb() is already imminent and the returned task_struct would could be used after free.) As for the fix, we cannot simply check the signal->live count of a task on the dying list because that won't distinguish regular zombies waiting to be reaped from RCU remnant tasks that are going to be free'd. Therefore add an extra check to rule out ->usage==0 tasks from any iteration. The repeat: loop in css_task_iter_advance() doesn't consider ->usage count, so add a new loop to css_task_iter_next() to skip de-used tasks on the dying_list. Rough illustration of the possible race R (reader of cgroup.procs) T (thread) L (group leader) --------------------------------- -------------------------------- -------------------------------- L exits, signal->live > 0 cgroup_task_dead(L) css_set_skip_task_iters() // skips only cset->tasks list_add_tail(&L->cg_list, &cset->dying_tasks) css_task_iter_next() take css_set_lock css_task_iter_advance() leader && signal->live != 0 => it->task_pos = &L->cg_list release css_set_lock T exits --signal->live == 0 cgroup_task_dead(T) // css_set_lock release_task(T) cgroup_task_release(T) release_task(L) // zap_leader cgroup_task_release(L) put_task_struct_rcu_user(L) ...RCU... put_task_struct(L) L->usage = 0 /* L still on dying_tasks */ ...RCU... __put_task_struct(L) css_task_iter_next() // another iteration take css_set_lock it->task_pos = &L->cg_list get_task_struct(L) => addition on 0 drop css_set_lock cgroup_task_free(L) css_set_skip_task_iters() // dying skip comes too late free_task(L) cgroup_procs_show() task_pid_vnr(L)•CVE-2026-98163