CVE-2025-38347

Published Jul 10, 2025

Last updated 5 months ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to do sanity check on ino and xnid syzbot reported a f2fs bug as below: INFO: task syz-executor140:5308 blocked for more than 143 seconds. Not tainted 6.14.0-rc7-syzkaller-00069-g81e4f8d68c66 #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor140 state:D stack:24016 pid:5308 tgid:5308 ppid:5306 task_flags:0x400140 flags:0x00000006 Call Trace: <TASK> context_switch kernel/sched/core.c:5378 [inline] __schedule+0x190e/0x4c90 kernel/sched/core.c:6765 __schedule_loop kernel/sched/core.c:6842 [inline] schedule+0x14b/0x320 kernel/sched/core.c:6857 io_schedule+0x8d/0x110 kernel/sched/core.c:7690 folio_wait_bit_common+0x839/0xee0 mm/filemap.c:1317 __folio_lock mm/filemap.c:1664 [inline] folio_lock include/linux/pagemap.h:1163 [inline] __filemap_get_folio+0x147/0xb40 mm/filemap.c:1917 pagecache_get_page+0x2c/0x130 mm/folio-compat.c:87 find_get_page_flags include/linux/pagemap.h:842 [inline] f2fs_grab_cache_page+0x2b/0x320 fs/f2fs/f2fs.h:2776 __get_node_page+0x131/0x11b0 fs/f2fs/node.c:1463 read_xattr_block+0xfb/0x190 fs/f2fs/xattr.c:306 lookup_all_xattrs fs/f2fs/xattr.c:355 [inline] f2fs_getxattr+0x676/0xf70 fs/f2fs/xattr.c:533 __f2fs_get_acl+0x52/0x870 fs/f2fs/acl.c:179 f2fs_acl_create fs/f2fs/acl.c:375 [inline] f2fs_init_acl+0xd7/0x9b0 fs/f2fs/acl.c:418 f2fs_init_inode_metadata+0xa0f/0x1050 fs/f2fs/dir.c:539 f2fs_add_inline_entry+0x448/0x860 fs/f2fs/inline.c:666 f2fs_add_dentry+0xba/0x1e0 fs/f2fs/dir.c:765 f2fs_do_add_link+0x28c/0x3a0 fs/f2fs/dir.c:808 f2fs_add_link fs/f2fs/f2fs.h:3616 [inline] f2fs_mknod+0x2e8/0x5b0 fs/f2fs/namei.c:766 vfs_mknod+0x36d/0x3b0 fs/namei.c:4191 unix_bind_bsd net/unix/af_unix.c:1286 [inline] unix_bind+0x563/0xe30 net/unix/af_unix.c:1379 __sys_bind_socket net/socket.c:1817 [inline] __sys_bind+0x1e4/0x290 net/socket.c:1848 __do_sys_bind net/socket.c:1853 [inline] __se_sys_bind net/socket.c:1851 [inline] __x64_sys_bind+0x7a/0x90 net/socket.c:1851 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f Let's dump and check metadata of corrupted inode, it shows its xattr_nid is the same to its i_ino. dump.f2fs -i 3 chaseyu.img.raw i_xattr_nid [0x 3 : 3] So that, during mknod in the corrupted directory, it tries to get and lock inode page twice, result in deadlock. - f2fs_mknod - f2fs_add_inline_entry - f2fs_get_inode_page --- lock dir's inode page - f2fs_init_acl - f2fs_acl_create(dir,..) - __f2fs_get_acl - f2fs_getxattr - lookup_all_xattrs - __get_node_page --- try to lock dir's inode page In order to fix this, let's add sanity check on ino and xnid.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Modified
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