KASAN: slab-use-after-free Read in udf_sync_fs

Status: upstream: reported syz repro on 2026/11/08 21:04
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+4bab437729c7601f6680@syzkaller.appspotmail.com
First crash: 4d04h, last: 4d04h
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/11/12 upstream (ToT) 9d66f26fefac syz [report] KASAN: use-after-free Read in udf_sync_fs
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in udf_sync_fs udf 19 syz, C done done 37 1050d 1188d 25/29 fixed on 2024/02/03 12:44
linux-5.15 KASAN: use-after-free Read in udf_sync_fs origin:upstream 19 syz, C error 26 45d 1245d 0/3 upstream: reported C repro on 2023/06/16 18:53
linux-6.6 KASAN: use-after-free Read in udf_sync_fs 19 1 326d 326d 0/2 auto-obsoleted due to no activity on 2026/03/31 04:31
linux-6.1 KASAN: use-after-free Read in udf_sync_fs origin:upstream 19 syz, C error 60 52d 1243d 0/3 upstream: reported C repro on 2023/06/18 11:33

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in crc_itu_t+0x1fe/0x290 lib/crc-itu-t.c:60
Read of size 1 at addr ffff888025fd8000 by task syz-executor/5933

CPU: 0 PID: 5933 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 crc_itu_t+0x1fe/0x290 lib/crc-itu-t.c:60
 udf_finalize_lvid fs/udf/super.c:2032 [inline]
 udf_sync_fs+0x194/0x3b0 fs/udf/super.c:2381
 sync_filesystem+0xea/0x220 fs/sync.c:56
 generic_shutdown_super+0x6f/0x2b0 fs/super.c:663
 kill_block_super+0x44/0x90 fs/super.c:1671
 deactivate_locked_super+0x9c/0x210 fs/super.c:479
 cleanup_mnt+0x3d7/0x460 fs/namespace.c:1259
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x986/0x2530 kernel/exit.c:890
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1032
 __do_sys_exit_group kernel/exit.c:1043 [inline]
 __se_sys_exit_group kernel/exit.c:1041 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1041
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f90e039fb19
Code: Unable to access opcode bytes at 0x7f90e039faef.
RSP: 002b:00007ffff05a8268 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f90e0436fd8 RCX: 00007f90e039fb19
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000005 R08: 0000000000000000 R09: 00007f90e0436fb3
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffff05a9520
R13: 00007f90e0436fb3 R14: 00000000000176b6 R15: 00007ffff05aa5f0
 </TASK>

Allocated by task 5151:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc+0xb7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 tomoyo_realpath_from_path+0xe6/0x5c0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x224/0x460 security/tomoyo/file.c:771
 security_file_open+0x62/0xa0 security/security.c:2968
 do_dentry_open+0x32b/0x14b0 fs/open.c:916
 do_open fs/namei.c:3695 [inline]
 path_openat+0x284f/0x3270 fs/namei.c:3856
 do_filp_open+0x1f2/0x430 fs/namei.c:3883
 do_sys_openat2+0x134/0x1d0 fs/open.c:1422
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1448
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 5151:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1833 [inline]
 slab_free_freelist_hook+0x154/0x240 mm/slub.c:1859
 slab_free mm/slub.c:3853 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3866
 tomoyo_realpath_from_path+0x587/0x5c0 security/tomoyo/realpath.c:286
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x224/0x460 security/tomoyo/file.c:771
 security_file_open+0x62/0xa0 security/security.c:2968
 do_dentry_open+0x32b/0x14b0 fs/open.c:916
 do_open fs/namei.c:3695 [inline]
 path_openat+0x284f/0x3270 fs/namei.c:3856
 do_filp_open+0x1f2/0x430 fs/namei.c:3883
 do_sys_openat2+0x134/0x1d0 fs/open.c:1422
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1448
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888025fd8000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 0 bytes inside of
 freed 4096-byte region [ffff888025fd8000, ffff888025fd9000)

The buggy address belongs to the physical page:
page:ffffea000097f600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x25fd8
head:ffffea000097f600 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888018c42140 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5151, tgid 5151 (udevd), ts 96311554367, free_ts 96281363289
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_slab_page+0x5d/0x180 mm/slub.c:1903
 allocate_slab mm/slub.c:2050 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2103
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3275
 __slab_alloc mm/slub.c:3361 [inline]
 __slab_alloc_node mm/slub.c:3414 [inline]
 slab_alloc_node mm/slub.c:3508 [inline]
 __kmem_cache_alloc_node+0x122/0x260 mm/slub.c:3557
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc+0xa7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 tomoyo_realpath_from_path+0xe6/0x5c0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x224/0x460 security/tomoyo/file.c:771
 security_file_open+0x62/0xa0 security/security.c:2968
 do_dentry_open+0x32b/0x14b0 fs/open.c:916
 do_open fs/namei.c:3695 [inline]
 path_openat+0x284f/0x3270 fs/namei.c:3856
 do_filp_open+0x1f2/0x430 fs/namei.c:3883
 do_sys_openat2+0x134/0x1d0 fs/open.c:1422
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1448
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 discard_slab mm/slub.c:2149 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2689
 put_cpu_partial+0x17c/0x250 mm/slub.c:2765
 __slab_free+0x319/0x400 mm/slub.c:3723
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
 slab_alloc_node mm/slub.c:3518 [inline]
 kmem_cache_alloc_node+0x1af/0x320 mm/slub.c:3563
 __alloc_skb+0x103/0x2c0 net/core/skbuff.c:643
 alloc_skb include/linux/skbuff.h:1316 [inline]
 nlmsg_new include/net/netlink.h:1010 [inline]
 netlink_ack+0x377/0x1160 net/netlink/af_netlink.c:2491
 netlink_rcv_skb+0x2b3/0x4c0 net/netlink/af_netlink.c:2560
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x856/0x9e0 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1903
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 __sys_sendto+0x4a9/0x6b0 net/socket.c:2201

Memory state around the buggy address:
 ffff888025fd7f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888025fd7f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888025fd8000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888025fd8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888025fd8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/11/08 21:04 linux-6.6.y 5139929c698c 5cecaf1f .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in udf_sync_fs
* Struck through repros no longer work on HEAD.