CVE-2025-38219

Published Jul 4, 2025

Last updated 10 months ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: f2fs: prevent kernel warning due to negative i_nlink from corrupted image WARNING: CPU: 1 PID: 9426 at fs/inode.c:417 drop_nlink+0xac/0xd0 home/cc/linux/fs/inode.c:417 Modules linked in: CPU: 1 UID: 0 PID: 9426 Comm: syz-executor568 Not tainted 6.14.0-12627-g94d471a4f428 #2 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 RIP: 0010:drop_nlink+0xac/0xd0 home/cc/linux/fs/inode.c:417 Code: 48 8b 5d 28 be 08 00 00 00 48 8d bb 70 07 00 00 e8 f9 67 e6 ff f0 48 ff 83 70 07 00 00 5b 5d e9 9a 12 82 ff e8 95 12 82 ff 90 &lt;0f&gt; 0b 90 c7 45 48 ff ff ff ff 5b 5d e9 83 12 82 ff e8 fe 5f e6 ff RSP: 0018:ffffc900026b7c28 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8239710f RDX: ffff888041345a00 RSI: ffffffff8239717b RDI: 0000000000000005 RBP: ffff888054509ad0 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000000 R11: ffffffff9ab36f08 R12: ffff88804bb40000 R13: ffff8880545091e0 R14: 0000000000008000 R15: ffff8880545091e0 FS: 000055555d0c5880(0000) GS:ffff8880eb3e3000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f915c55b178 CR3: 0000000050d20000 CR4: 0000000000352ef0 Call Trace: <task> f2fs_i_links_write home/cc/linux/fs/f2fs/f2fs.h:3194 [inline] f2fs_drop_nlink+0xd1/0x3c0 home/cc/linux/fs/f2fs/dir.c:845 f2fs_delete_entry+0x542/0x1450 home/cc/linux/fs/f2fs/dir.c:909 f2fs_unlink+0x45c/0x890 home/cc/linux/fs/f2fs/namei.c:581 vfs_unlink+0x2fb/0x9b0 home/cc/linux/fs/namei.c:4544 do_unlinkat+0x4c5/0x6a0 home/cc/linux/fs/namei.c:4608 __do_sys_unlink home/cc/linux/fs/namei.c:4654 [inline] __se_sys_unlink home/cc/linux/fs/namei.c:4652 [inline] __x64_sys_unlink+0xc5/0x110 home/cc/linux/fs/namei.c:4652 do_syscall_x64 home/cc/linux/arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc7/0x250 home/cc/linux/arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fb3d092324b Code: 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 57 00 00 00 0f 05 &lt;48&gt; 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffdc232d938 EFLAGS: 00000206 ORIG_RAX: 0000000000000057 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb3d092324b RDX: 00007ffdc232d960 RSI: 00007ffdc232d960 RDI: 00007ffdc232d9f0 RBP: 00007ffdc232d9f0 R08: 0000000000000001 R09: 00007ffdc232d7c0 R10: 00000000fffffffd R11: 0000000000000206 R12: 00007ffdc232eaf0 R13: 000055555d0cebb0 R14: 00007ffdc232d958 R15: 0000000000000001 </task>
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Analyzed
Products
linux_kernel, debian_linux

Risk scores

CVSS 3.1

Type
Primary
Base score
5.5
Impact score
3.6
Exploitability score
1.8
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Severity
MEDIUM

Weaknesses

nvd@nist.gov
NVD-CWE-noinfo

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