CVE-2025-38459

Published Jul 25, 2025

Last updated 10 months ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: atm: clip: Fix infinite recursive call of clip_push(). syzbot reported the splat below. [0] This happens if we call ioctl(ATMARP_MKIP) more than once. During the first call, clip_mkip() sets clip_push() to vcc->push(), and the second call copies it to clip_vcc->old_push(). Later, when the socket is close()d, vcc_destroy_socket() passes NULL skb to clip_push(), which calls clip_vcc->old_push(), triggering the infinite recursion. Let's prevent the second ioctl(ATMARP_MKIP) by checking vcc->user_back, which is allocated by the first call as clip_vcc. Note also that we use lock_sock() to prevent racy calls. [0]: BUG: TASK stack guard page was hit at ffffc9000d66fff8 (stack is ffffc9000d670000..ffffc9000d678000) Oops: stack guard page: 0000 [#1] SMP KASAN NOPTI CPU: 0 UID: 0 PID: 5322 Comm: syz.0.0 Not tainted 6.16.0-rc4-syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:clip_push+0x5/0x720 net/atm/clip.c:191 Code: e0 8f aa 8c e8 1c ad 5b fa eb ae 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 <41> 57 41 56 41 55 41 54 53 48 83 ec 20 48 89 f3 49 89 fd 48 bd 00 RSP: 0018:ffffc9000d670000 EFLAGS: 00010246 RAX: 1ffff1100235a4a5 RBX: ffff888011ad2508 RCX: ffff8880003c0000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888037f01000 RBP: dffffc0000000000 R08: ffffffff8fa104f7 R09: 1ffffffff1f4209e R10: dffffc0000000000 R11: ffffffff8a99b300 R12: ffffffff8a99b300 R13: ffff888037f01000 R14: ffff888011ad2500 R15: ffff888037f01578 FS: 000055557ab6d500(0000) GS:ffff88808d250000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffc9000d66fff8 CR3: 0000000043172000 CR4: 0000000000352ef0 Call Trace: <TASK> clip_push+0x6dc/0x720 net/atm/clip.c:200 clip_push+0x6dc/0x720 net/atm/clip.c:200 clip_push+0x6dc/0x720 net/atm/clip.c:200 ... clip_push+0x6dc/0x720 net/atm/clip.c:200 clip_push+0x6dc/0x720 net/atm/clip.c:200 clip_push+0x6dc/0x720 net/atm/clip.c:200 vcc_destroy_socket net/atm/common.c:183 [inline] vcc_release+0x157/0x460 net/atm/common.c:205 __sock_release net/socket.c:647 [inline] sock_close+0xc0/0x240 net/socket.c:1391 __fput+0x449/0xa70 fs/file_table.c:465 task_work_run+0x1d1/0x260 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:114 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline] do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ff31c98e929 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fffb5aa1f78 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 0000000000012747 RCX: 00007ff31c98e929 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007ff31cbb7ba0 R08: 0000000000000001 R09: 0000000db5aa226f R10: 00007ff31c7ff030 R11: 0000000000000246 R12: 00007ff31cbb608c R13: 00007ff31cbb6080 R14: ffffffffffffffff R15: 00007fffb5aa2090 </TASK> Modules linked in:
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Analyzed
Products
linux_kernel, debian_linux

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-674

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