CVE-2022-49511

Published Feb 26, 2025

Last updated 3 months ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: fbdev: defio: fix the pagelist corruption Easily hit the below list corruption: == list_add corruption. prev->next should be next (ffffffffc0ceb090), but was ffffec604507edc8. (prev=ffffec604507edc8). WARNING: CPU: 65 PID: 3959 at lib/list_debug.c:26 __list_add_valid+0x53/0x80 CPU: 65 PID: 3959 Comm: fbdev Tainted: G U RIP: 0010:__list_add_valid+0x53/0x80 Call Trace: <TASK> fb_deferred_io_mkwrite+0xea/0x150 do_page_mkwrite+0x57/0xc0 do_wp_page+0x278/0x2f0 __handle_mm_fault+0xdc2/0x1590 handle_mm_fault+0xdd/0x2c0 do_user_addr_fault+0x1d3/0x650 exc_page_fault+0x77/0x180 ? asm_exc_page_fault+0x8/0x30 asm_exc_page_fault+0x1e/0x30 RIP: 0033:0x7fd98fc8fad1 == Figure out the race happens when one process is adding &page->lru into the pagelist tail in fb_deferred_io_mkwrite(), another process is re-initializing the same &page->lru in fb_deferred_io_fault(), which is not protected by the lock. This fix is to init all the page lists one time during initialization, it not only fixes the list corruption, but also avoids INIT_LIST_HEAD() redundantly. V2: change "int i" to "unsigned int i" (Geert Uytterhoeven)
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Modified
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
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