CVE-2023-53089

Published May 2, 2025

Last updated a year ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: ext4: fix task hung in ext4_xattr_delete_inode Syzbot reported a hung task problem: ================================================================== INFO: task syz-executor232:5073 blocked for more than 143 seconds. Not tainted 6.2.0-rc2-syzkaller-00024-g512dee0c00ad #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-exec232 state:D stack:21024 pid:5073 ppid:5072 flags:0x00004004 Call Trace: <TASK> context_switch kernel/sched/core.c:5244 [inline] __schedule+0x995/0xe20 kernel/sched/core.c:6555 schedule+0xcb/0x190 kernel/sched/core.c:6631 __wait_on_freeing_inode fs/inode.c:2196 [inline] find_inode_fast+0x35a/0x4c0 fs/inode.c:950 iget_locked+0xb1/0x830 fs/inode.c:1273 __ext4_iget+0x22e/0x3ed0 fs/ext4/inode.c:4861 ext4_xattr_inode_iget+0x68/0x4e0 fs/ext4/xattr.c:389 ext4_xattr_inode_dec_ref_all+0x1a7/0xe50 fs/ext4/xattr.c:1148 ext4_xattr_delete_inode+0xb04/0xcd0 fs/ext4/xattr.c:2880 ext4_evict_inode+0xd7c/0x10b0 fs/ext4/inode.c:296 evict+0x2a4/0x620 fs/inode.c:664 ext4_orphan_cleanup+0xb60/0x1340 fs/ext4/orphan.c:474 __ext4_fill_super fs/ext4/super.c:5516 [inline] ext4_fill_super+0x81cd/0x8700 fs/ext4/super.c:5644 get_tree_bdev+0x400/0x620 fs/super.c:1282 vfs_get_tree+0x88/0x270 fs/super.c:1489 do_new_mount+0x289/0xad0 fs/namespace.c:3145 do_mount fs/namespace.c:3488 [inline] __do_sys_mount fs/namespace.c:3697 [inline] __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7fa5406fd5ea RSP: 002b:00007ffc7232f968 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fa5406fd5ea RDX: 0000000020000440 RSI: 0000000020000000 RDI: 00007ffc7232f970 RBP: 00007ffc7232f970 R08: 00007ffc7232f9b0 R09: 0000000000000432 R10: 0000000000804a03 R11: 0000000000000202 R12: 0000000000000004 R13: 0000555556a7a2c0 R14: 00007ffc7232f9b0 R15: 0000000000000000 </TASK> ================================================================== The problem is that the inode contains an xattr entry with ea_inum of 15 when cleaning up an orphan inode <15>. When evict inode <15>, the reference counting of the corresponding EA inode is decreased. When EA inode <15> is found by find_inode_fast() in __ext4_iget(), it is found that the EA inode holds the I_FREEING flag and waits for the EA inode to complete deletion. As a result, when inode <15> is being deleted, we wait for inode <15> to complete the deletion, resulting in an infinite loop and triggering Hung Task. To solve this problem, we only need to check whether the ino of EA inode and parent is the same before getting EA inode.
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-835

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