KASAN: use-after-free Read in f2fs_write_end_io (2)

Status: fixed on 2026/05/06 16:40
Subsystems: f2fs
[Documentation on labels]
Reported-by: syzbot+b4444e3c972a7a124187@syzkaller.appspotmail.com
Fix commit: ce2739e482bc f2fs: fix to avoid UAF in f2fs_write_end_io()
First crash: 224d, last: 165d
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[PATCH] f2fs: fix to avoid UAF in f2fs_write_end_io() 3 (3) 2026/03/02 01:31
[syzbot] [f2fs?] KASAN: use-after-free Read in f2fs_write_end_io (2) 3 (9) 2026/01/07 11:14
[PATCH] f2fs: fix use-after-free in f2fs_write_end_io 10 (10) 2026/01/07 07:06
[PATCH v4] f2fs: fix use-after-free in f2fs_write_end_io 1 (1) 2025/12/30 14:02
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in f2fs_write_end_io f2fs 19 1 1447d 1439d 0/29 auto-obsoleted due to no activity on 2022/12/06 18:50
android-5-10 KASAN: use-after-free Read in f2fs_write_end_io 19 1 839d 839d 0/2 auto-obsoleted due to no activity on 2024/07/06 04:33
upstream KASAN: slab-use-after-free Read in f2fs_write_end_io f2fs 19 2 339d 337d 0/29 auto-obsoleted due to no activity on 2025/11/18 10:59
▶ ▼ Last patch testing requests (5)
Created Duration User Patch Repo Result
2026/01/07 10:59 13m chao@kernel.org https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/syzbot error
2026/01/07 09:50 13m chao@kernel.org https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/syzbot error
2026/01/07 08:49 20m chao@kernel.org https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/syzbot OK log
2026/01/07 06:44 14m chao@kernel.org https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/syzbot report log
2026/01/07 02:04 14m chao@kernel.org https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/syzbot error

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: slab-use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
BUG: KASAN: slab-use-after-free in get_pages fs/f2fs/f2fs.h:2718 [inline]
BUG: KASAN: slab-use-after-free in f2fs_write_end_io+0x9b9/0xb60 fs/f2fs/data.c:364
Read of size 4 at addr ffff88804357d170 by task kworker/u4:4/45

CPU: 0 UID: 0 PID: 45 Comm: kworker/u4:4 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: loop0 loop_workfn
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
 get_pages fs/f2fs/f2fs.h:2718 [inline]
 f2fs_write_end_io+0x9b9/0xb60 fs/f2fs/data.c:364
 blk_update_request+0x57e/0xe60 block/blk-mq.c:1007
 blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1169
 lo_rw_aio_complete drivers/block/loop.c:337 [inline]
 lo_rw_aio+0xcd1/0xef0 drivers/block/loop.c:410
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1926 [inline]
 loop_process_work+0x8fe/0x10b0 drivers/block/loop.c:1961
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>

Allocated by task 5484:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:397 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:414
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __kmalloc_cache_noprof+0x3e2/0x700 mm/slub.c:5776
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 f2fs_fill_super+0x8c/0x6ec0 fs/f2fs/super.c:4895
 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
 vfs_get_tree+0x92/0x2a0 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount+0x302/0xa10 fs/namespace.c:3712
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x313/0x410 fs/namespace.c:4201
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5484:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6670 [inline]
 kfree+0x1c0/0x660 mm/slub.c:6878
 kill_f2fs_super+0x5b6/0x6c0 fs/f2fs/super.c:5458
 deactivate_locked_super+0xbc/0x130 fs/super.c:474
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1318
 task_work_run+0x1d4/0x260 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x694/0x22f0 kernel/exit.c:971
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1112
 __do_sys_exit_group kernel/exit.c:1123 [inline]
 __se_sys_exit_group kernel/exit.c:1121 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1121
 __pfx_syscall_get_nr+0x0/0x10 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:56
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 insert_work+0x3d/0x330 kernel/workqueue.c:2180
 __queue_work+0xcd0/0xf90 kernel/workqueue.c:2335
 queue_work_on+0x106/0x1c0 kernel/workqueue.c:2386
 queue_work include/linux/workqueue.h:669 [inline]
 schedule_work include/linux/workqueue.h:730 [inline]
 f2fs_handle_critical_error+0x255/0x540 fs/f2fs/super.c:4624
 f2fs_write_end_io+0x886/0xb60 fs/f2fs/data.c:351
 __submit_merged_bio+0x256/0x660 fs/f2fs/data.c:540
 __f2fs_submit_merged_write fs/f2fs/data.c:635 [inline]
 __submit_merged_write_cond+0x471/0x530 fs/f2fs/data.c:657
 f2fs_sync_node_pages+0x1479/0x15e0 fs/f2fs/node.c:2166
 block_operations fs/f2fs/checkpoint.c:1276 [inline]
 f2fs_write_checkpoint+0xdd5/0x2430 fs/f2fs/checkpoint.c:1678
 kill_f2fs_super+0x2d2/0x6c0 fs/f2fs/super.c:5448
 deactivate_locked_super+0xbc/0x130 fs/super.c:474
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1318
 task_work_run+0x1d4/0x260 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x694/0x22f0 kernel/exit.c:971
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1112
 __do_sys_exit_group kernel/exit.c:1123 [inline]
 __se_sys_exit_group kernel/exit.c:1121 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1121
 __pfx_syscall_get_nr+0x0/0x10 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:56
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 insert_work+0x3d/0x330 kernel/workqueue.c:2180
 __queue_work+0xcd0/0xf90 kernel/workqueue.c:2335
 queue_work_on+0x106/0x1c0 kernel/workqueue.c:2386
 sanity_check_node_footer fs/f2fs/node.c:1536 [inline]
 __get_node_folio+0xcaf/0x14f0 fs/f2fs/node.c:1581
 do_read_inode fs/f2fs/inode.c:425 [inline]
 f2fs_iget+0x77c/0x5640 fs/f2fs/inode.c:596
 f2fs_nfs_get_inode+0x76/0x110 fs/f2fs/super.c:3723
 generic_fh_to_dentry+0x9f/0xf0 fs/libfs.c:1498
 exportfs_decode_fh_raw+0x178/0x6e0 fs/exportfs/expfs.c:456
 do_handle_to_path+0xa4/0x1a0 fs/fhandle.c:276
 handle_to_path fs/fhandle.c:400 [inline]
 do_handle_open+0x6a1/0x930 fs/fhandle.c:424
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88804357c000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 4464 bytes inside of
 freed 8192-byte region [ffff88804357c000, ffff88804357e000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x43578
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000040 ffff88801a442280 ffffea000046b000 0000000000000002
raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 04fff00000000040 ffff88801a442280 ffffea000046b000 0000000000000002
head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 04fff00000000003 ffffea00010d5e01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x528c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NORETRY|__GFP_COMP), pid 5411, tgid 5411 (syz-executor), ts 97414573985, free_ts 95403368329
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1846
 prep_new_page mm/page_alloc.c:1854 [inline]
 get_page_from_freelist+0x24e0/0x2580 mm/page_alloc.c:3915
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3b0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xe53/0x1820 mm/slub.c:4656
 __slab_alloc+0x65/0x100 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 __do_kmalloc_node mm/slub.c:5656 [inline]
 __kvmalloc_node_noprof+0x6b6/0x920 mm/slub.c:7136
 kvmalloc_array_node_noprof include/linux/slab.h:1122 [inline]
 __ptr_ring_init_queue_alloc_noprof include/linux/ptr_ring.h:481 [inline]
 ptr_ring_init_noprof include/linux/ptr_ring.h:499 [inline]
 wg_packet_queue_init+0xbc/0x320 drivers/net/wireguard/queueing.c:32
 wg_newlink+0x2f6/0x670 drivers/net/wireguard/device.c:352
 rtnl_newlink_create+0x310/0xb00 net/core/rtnetlink.c:3840
 __rtnl_newlink net/core/rtnetlink.c:3957 [inline]
 rtnl_newlink+0x16e7/0x1c90 net/core/rtnetlink.c:4072
 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
page last free pid 4363 tgid 4363 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2943
 unix_net_exit+0x6b/0xb0 net/unix/af_unix.c:3837
 ops_exit_list net/core/net_namespace.c:199 [inline]
 ops_undo_list+0x49a/0x990 net/core/net_namespace.c:252
 cleanup_net+0x4d8/0x7a0 net/core/net_namespace.c:696
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Memory state around the buggy address:
 ffff88804357d000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804357d080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88804357d100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                             ^
 ffff88804357d180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804357d200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/22 04:07 upstream 765b233a9b94 d1b870e1 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in f2fs_write_end_io
2026/02/10 00:52 upstream 05f7e89ab973 4ab09a02 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in f2fs_write_end_io
2026/01/28 13:36 upstream 1f97d9dcf536 004c195c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in f2fs_write_end_io
2026/01/27 15:25 upstream fcb70a56f4d8 9a514c2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in f2fs_write_end_io
2026/01/14 09:45 upstream c537e12daeec d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in f2fs_write_end_io
2025/12/20 21:47 upstream d8ba32c5a460 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in f2fs_write_end_io
2025/12/13 14:51 upstream 9551a26f17d9 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in f2fs_write_end_io
2026/01/25 06:44 upstream 5dbeeb268b63 40acda8a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in f2fs_write_end_io
2026/01/16 10:59 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in f2fs_write_end_io
2026/01/10 13:18 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in f2fs_write_end_io
2026/01/02 16:56 upstream b69053dd3ffb d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in f2fs_write_end_io
2025/12/28 23:30 upstream c875a6c32467 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in f2fs_write_end_io
2025/12/23 23:01 upstream b927546677c8 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in f2fs_write_end_io
2025/12/22 02:41 upstream 765b233a9b94 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in f2fs_write_end_io
* Struck through repros no longer work on HEAD.