CVE-2025-38578

Published Aug 19, 2025

Last updated 3 months ago

CVSS high 7.8

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid UAF in f2fs_sync_inode_meta() syzbot reported an UAF issue as below: [1] [2] [1] https://syzkaller.appspot.com/text?tag=CrashReport&x=16594c60580000 ================================================================== BUG: KASAN: use-after-free in __list_del_entry_valid+0xa6/0x130 lib/list_debug.c:62 Read of size 8 at addr ffff888100567dc8 by task kworker/u4:0/8 CPU: 1 PID: 8 Comm: kworker/u4:0 Tainted: G W 6.1.129-syzkaller-00017-g642656a36791 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Workqueue: writeback wb_workfn (flush-7:0) Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:316 [inline] print_report+0x158/0x4e0 mm/kasan/report.c:427 kasan_report+0x13c/0x170 mm/kasan/report.c:531 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351 __list_del_entry_valid+0xa6/0x130 lib/list_debug.c:62 __list_del_entry include/linux/list.h:134 [inline] list_del_init include/linux/list.h:206 [inline] f2fs_inode_synced+0x100/0x2e0 fs/f2fs/super.c:1553 f2fs_update_inode+0x72/0x1c40 fs/f2fs/inode.c:588 f2fs_update_inode_page+0x135/0x170 fs/f2fs/inode.c:706 f2fs_write_inode+0x416/0x790 fs/f2fs/inode.c:734 write_inode fs/fs-writeback.c:1460 [inline] __writeback_single_inode+0x4cf/0xb80 fs/fs-writeback.c:1677 writeback_sb_inodes+0xb32/0x1910 fs/fs-writeback.c:1903 __writeback_inodes_wb+0x118/0x3f0 fs/fs-writeback.c:1974 wb_writeback+0x3da/0xa00 fs/fs-writeback.c:2081 wb_check_background_flush fs/fs-writeback.c:2151 [inline] wb_do_writeback fs/fs-writeback.c:2239 [inline] wb_workfn+0xbba/0x1030 fs/fs-writeback.c:2266 process_one_work+0x73d/0xcb0 kernel/workqueue.c:2299 worker_thread+0xa60/0x1260 kernel/workqueue.c:2446 kthread+0x26d/0x300 kernel/kthread.c:386 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> Allocated by task 298: kasan_save_stack mm/kasan/common.c:45 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:52 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:333 kasan_slab_alloc include/linux/kasan.h:202 [inline] slab_post_alloc_hook+0x53/0x2c0 mm/slab.h:768 slab_alloc_node mm/slub.c:3421 [inline] slab_alloc mm/slub.c:3431 [inline] __kmem_cache_alloc_lru mm/slub.c:3438 [inline] kmem_cache_alloc_lru+0x102/0x270 mm/slub.c:3454 alloc_inode_sb include/linux/fs.h:3255 [inline] f2fs_alloc_inode+0x2d/0x350 fs/f2fs/super.c:1437 alloc_inode fs/inode.c:261 [inline] iget_locked+0x18c/0x7e0 fs/inode.c:1373 f2fs_iget+0x55/0x4ca0 fs/f2fs/inode.c:486 f2fs_lookup+0x3c1/0xb50 fs/f2fs/namei.c:484 __lookup_slow+0x2b9/0x3e0 fs/namei.c:1689 lookup_slow+0x5a/0x80 fs/namei.c:1706 walk_component+0x2e7/0x410 fs/namei.c:1997 lookup_last fs/namei.c:2454 [inline] path_lookupat+0x16d/0x450 fs/namei.c:2478 filename_lookup+0x251/0x600 fs/namei.c:2507 vfs_statx+0x107/0x4b0 fs/stat.c:229 vfs_fstatat fs/stat.c:267 [inline] vfs_lstat include/linux/fs.h:3434 [inline] __do_sys_newlstat fs/stat.c:423 [inline] __se_sys_newlstat+0xda/0x7c0 fs/stat.c:417 __x64_sys_newlstat+0x5b/0x70 fs/stat.c:417 x64_sys_call+0x52/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:7 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x3b/0x80 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x68/0xd2 Freed by task 0: kasan_save_stack mm/kasan/common.c:45 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:52 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516 ____kasan_slab_free+0x131/0x180 mm/kasan/common.c:241 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:249 kasan_slab_free include/linux/kasan.h:178 [inline] slab_free_hook mm/slub.c:1745 [inline] slab_free_freelist_hook mm/slub.c:1771 [inline] slab_free mm/slub.c:3686 [inline] kmem_cache_free+0x ---truncated---
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
CWE-416

Social media

Hype score
Not currently trending

Configurations

Related CVEs

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  2. 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
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References

Sources include official advisories and independent security research.