CVE-2022-50126

Published Jun 18, 2025

Last updated a year ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: jbd2: fix assertion 'jh->b_frozen_data == NULL' failure when journal aborted Following process will fail assertion 'jh->b_frozen_data == NULL' in jbd2_journal_dirty_metadata(): jbd2_journal_commit_transaction unlink(dir/a) jh->b_transaction = trans1 jh->b_jlist = BJ_Metadata journal->j_running_transaction = NULL trans1->t_state = T_COMMIT unlink(dir/b) handle->h_trans = trans2 do_get_write_access jh->b_modified = 0 jh->b_frozen_data = frozen_buffer jh->b_next_transaction = trans2 jbd2_journal_dirty_metadata is_handle_aborted is_journal_aborted // return false --> jbd2 abort <-- while (commit_transaction->t_buffers) if (is_journal_aborted) jbd2_journal_refile_buffer __jbd2_journal_refile_buffer WRITE_ONCE(jh->b_transaction, jh->b_next_transaction) WRITE_ONCE(jh->b_next_transaction, NULL) __jbd2_journal_file_buffer(jh, BJ_Reserved) J_ASSERT_JH(jh, jh->b_frozen_data == NULL) // assertion failure ! The reproducer (See detail in [Link]) reports: ------------[ cut here ]------------ kernel BUG at fs/jbd2/transaction.c:1629! invalid opcode: 0000 [#1] PREEMPT SMP CPU: 2 PID: 584 Comm: unlink Tainted: G W 5.19.0-rc6-00115-g4a57a8400075-dirty #697 RIP: 0010:jbd2_journal_dirty_metadata+0x3c5/0x470 RSP: 0018:ffffc90000be7ce0 EFLAGS: 00010202 Call Trace: <TASK> __ext4_handle_dirty_metadata+0xa0/0x290 ext4_handle_dirty_dirblock+0x10c/0x1d0 ext4_delete_entry+0x104/0x200 __ext4_unlink+0x22b/0x360 ext4_unlink+0x275/0x390 vfs_unlink+0x20b/0x4c0 do_unlinkat+0x42f/0x4c0 __x64_sys_unlink+0x37/0x50 do_syscall_64+0x35/0x80 After journal aborting, __jbd2_journal_refile_buffer() is executed with holding @jh->b_state_lock, we can fix it by moving 'is_handle_aborted()' into the area protected by @jh->b_state_lock.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Analyzed
Products
linux_kernel

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
CWE-617

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