KASAN: use-after-free Read in __ocfs2_flush_truncate_log

Status: upstream: reported C repro on 2026/06/07 20:02
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+94da2b9a99715122ce75@syzkaller.appspotmail.com
First crash: 83d, last: 4d05h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/08/20 linux-6.1.y (ToT) 7e6e67054721 C [report] kernel BUG in _ocfs2_free_suballoc_bits
2026/08/20 upstream (ToT) a4ff2be345d0 C Didn't crash
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in __ocfs2_flush_truncate_log ocfs2 prio:high 19 syz, C inconclusive inconclusive 41 263d 700d 0/29 auto-obsoleted due to no activity on 2026/06/12 00:20
linux-5.15 KASAN: use-after-free Read in __ocfs2_flush_truncate_log origin:lts-only 19 syz, C error 6 4d07h 462d 0/3 upstream: reported C repro on 2025/05/25 11:09
linux-6.6 KASAN: use-after-free Read in __ocfs2_flush_truncate_log 19 syz, C 3 6d05h 6d06h 0/2 upstream: reported C repro on 2026/08/24 09:55

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in ocfs2_replay_truncate_records fs/ocfs2/alloc.c:5959 [inline]
BUG: KASAN: use-after-free in __ocfs2_flush_truncate_log+0x670/0x10a4 fs/ocfs2/alloc.c:6054
Read of size 4 at addr ffff0000d49d22c0 by task syz-executor/4450

CPU: 0 PID: 4450 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 __asan_report_load4_noabort+0x2c/0x38 mm/kasan/report_generic.c:350
 ocfs2_replay_truncate_records fs/ocfs2/alloc.c:5959 [inline]
 __ocfs2_flush_truncate_log+0x670/0x10a4 fs/ocfs2/alloc.c:6054
 ocfs2_flush_truncate_log+0x4c/0x6c fs/ocfs2/alloc.c:6076
 ocfs2_sync_fs+0x100/0x2c0 fs/ocfs2/super.c:402
 sync_filesystem+0x1a0/0x218 fs/sync.c:66
 generic_shutdown_super+0x74/0x32c fs/super.c:474
 kill_block_super+0x78/0xe0 fs/super.c:1470
 deactivate_locked_super+0xb4/0x128 fs/super.c:332
 deactivate_super+0xe4/0x104 fs/super.c:363
 cleanup_mnt+0x3a8/0x430 fs/namespace.c:1191
 __cleanup_mnt+0x20/0x30 fs/namespace.c:1198
 task_work_run+0x1f4/0x280 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
 el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Allocated by task 4461:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:936 [inline]
 __kmalloc_node_track_caller+0xcc/0x174 mm/slab_common.c:956
 kmalloc_reserve net/core/skbuff.c:446 [inline]
 __alloc_skb+0x260/0x728 net/core/skbuff.c:515
 alloc_skb include/linux/skbuff.h:1303 [inline]
 nlmsg_new include/net/netlink.h:998 [inline]
 rtmsg_ifinfo_build_skb+0x90/0x1b4 net/core/rtnetlink.c:3972
 rtmsg_ifinfo_event net/core/rtnetlink.c:4010 [inline]
 rtnetlink_event+0xd4/0x19c net/core/rtnetlink.c:6209
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xd8/0x168 kernel/notifier.c:455
 call_netdevice_notifiers_info+0xd0/0x120 net/core/dev.c:2014
 __netdev_upper_dev_link+0x430/0x5a8 net/core/dev.c:7788
 netdev_upper_dev_link+0xb4/0x100 net/core/dev.c:7829
 ipvlan_link_new+0x4e0/0x82c drivers/net/ipvlan/ipvlan_main.c:620
 rtnl_newlink_create net/core/rtnetlink.c:3428 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3648 [inline]
 rtnl_newlink+0x10b4/0x1af0 net/core/rtnetlink.c:3661
 rtnetlink_rcv_msg+0x694/0xcc4 net/core/rtnetlink.c:6158
 netlink_rcv_skb+0x220/0x3ec net/netlink/af_netlink.c:2516
 rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:6176
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5fc/0x80c net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x6f0/0x9d8 net/netlink/af_netlink.c:1877
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 __sys_sendto+0x324/0x440 net/socket.c:2153
 __do_sys_sendto net/socket.c:2165 [inline]
 __se_sys_sendto net/socket.c:2161 [inline]
 __arm64_sys_sendto+0xe4/0x104 net/socket.c:2161
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Freed by task 4461:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:516
 ____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:237
 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:245
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x16c/0x1e8 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xbc/0x21c mm/slub.c:3700
 kfree+0xd0/0x1a8 mm/slab_common.c:988
 skb_free_head net/core/skbuff.c:762 [inline]
 pskb_expand_head+0x344/0x1050 net/core/skbuff.c:1881
 netlink_trim+0x158/0x1fc net/netlink/af_netlink.c:1299
 netlink_broadcast+0x74/0x1054 net/netlink/af_netlink.c:1505
 nlmsg_multicast include/net/netlink.h:1078 [inline]
 nlmsg_notify+0xf0/0x1d4 net/netlink/af_netlink.c:2559
 rtnl_notify net/core/rtnetlink.c:799 [inline]
 rtmsg_ifinfo_send net/core/rtnetlink.c:3997 [inline]
 rtmsg_ifinfo_event net/core/rtnetlink.c:4013 [inline]
 rtnetlink_event+0x134/0x19c net/core/rtnetlink.c:6209
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xd8/0x168 kernel/notifier.c:455
 call_netdevice_notifiers_info+0xd0/0x120 net/core/dev.c:2014
 __netdev_upper_dev_link+0x430/0x5a8 net/core/dev.c:7788
 netdev_upper_dev_link+0xb4/0x100 net/core/dev.c:7829
 ipvlan_link_new+0x4e0/0x82c drivers/net/ipvlan/ipvlan_main.c:620
 rtnl_newlink_create net/core/rtnetlink.c:3428 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3648 [inline]
 rtnl_newlink+0x10b4/0x1af0 net/core/rtnetlink.c:3661
 rtnetlink_rcv_msg+0x694/0xcc4 net/core/rtnetlink.c:6158
 netlink_rcv_skb+0x220/0x3ec net/netlink/af_netlink.c:2516
 rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:6176
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5fc/0x80c net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x6f0/0x9d8 net/netlink/af_netlink.c:1877
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 __sys_sendto+0x324/0x440 net/socket.c:2153
 __do_sys_sendto net/socket.c:2165 [inline]
 __se_sys_sendto net/socket.c:2161 [inline]
 __arm64_sys_sendto+0xe4/0x104 net/socket.c:2161
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the object at ffff0000d49d2000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 704 bytes inside of
 4096-byte region [ffff0000d49d2000, ffff0000d49d3000)

The buggy address belongs to the physical page:
page:0000000080bfb2fa refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1149d0
head:0000000080bfb2fa order:3 compound_mapcount:0 compound_pincount:0
flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000010200 0000000000000000 dead000000000001 ffff0000c0002a80
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000d49d2180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d49d2200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff0000d49d2280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff0000d49d2300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d49d2380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
kernel BUG at fs/ocfs2/suballoc.c:2501!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4450 Comm: syz-executor Tainted: G    B              syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : _ocfs2_free_suballoc_bits+0xd84/0x1124 fs/ocfs2/suballoc.c:2501
lr : _ocfs2_free_suballoc_bits+0xd84/0x1124 fs/ocfs2/suballoc.c:2501
sp : ffff800021057380
x29: ffff8000210574c0 x28: ffff0000e157c000 x27: 000000000000088c
x26: 00000000003f0000 x25: ffff800009e669e4 x24: 0000000000010088
x23: ffff70000420ae7c x22: ffff0000d06a5e00 x21: 0000000000000e00
x20: 0000000000000e00 x19: dfff800000000000 x18: 1fffe00033e7277e
x17: ffff80001537d000 x16: ffff800011b8ee98 x15: 0000000000000000
x14: 00000000fffffffc x13: 0000000000ff0100 x12: 0000000000000000
x11: ff00800009e6c6d4 x10: 0000000000000000 x9 : ffff800009e6c6d4
x8 : ffff0000d048b800 x7 : 0000000000000000 x6 : ffff800009e669e4
x5 : 0000000000010088 x4 : 00000000003f0000 x3 : 000000000000088c
x2 : ffff0000e157c000 x1 : 0000000000000e00 x0 : 0000000000010914
Call trace:
 _ocfs2_free_suballoc_bits+0xd84/0x1124 fs/ocfs2/suballoc.c:2501
 _ocfs2_free_clusters+0x534/0xa4c fs/ocfs2/suballoc.c:2601
 ocfs2_free_clusters+0x50/0x68 fs/ocfs2/suballoc.c:2622
 ocfs2_replay_truncate_records fs/ocfs2/alloc.c:5971 [inline]
 __ocfs2_flush_truncate_log+0x5e0/0x10a4 fs/ocfs2/alloc.c:6054
 ocfs2_flush_truncate_log+0x4c/0x6c fs/ocfs2/alloc.c:6076
 ocfs2_sync_fs+0x100/0x2c0 fs/ocfs2/super.c:402
 sync_filesystem+0x1a0/0x218 fs/sync.c:66
 generic_shutdown_super+0x74/0x32c fs/super.c:474
 kill_block_super+0x78/0xe0 fs/super.c:1470
 deactivate_locked_super+0xb4/0x128 fs/super.c:332
 deactivate_super+0xe4/0x104 fs/super.c:363
 cleanup_mnt+0x3a8/0x430 fs/namespace.c:1191
 __cleanup_mnt+0x20/0x30 fs/namespace.c:1198
 task_work_run+0x1f4/0x280 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
 el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: 17fffe98 979917e0 d4210000 979917de (d4210000) 
---[ end trace 0000000000000000 ]---

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/22 07:30 linux-6.1.y 090666d3cc90 b561ce9c .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/06/23 03:19 linux-6.1.y fdb6fcb41cc7 5a630be6 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/06/07 20:01 linux-6.1.y 228da13e907e cc095639 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/07/21 21:55 linux-6.1.y 090666d3cc90 7c5de9c3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __ocfs2_flush_truncate_log
2026/08/26 10:56 linux-6.1.y 05208478041c 6a91adb4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/08/26 10:53 linux-6.1.y 05208478041c 6a91adb4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/08/26 10:53 linux-6.1.y 05208478041c 6a91adb4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/08/26 08:04 linux-6.1.y 05208478041c 6a91adb4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/08/24 20:48 linux-6.1.y 05208478041c b55bd4c3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/08/24 08:00 linux-6.1.y 05208478041c 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2026/08/24 07:55 linux-6.1.y 05208478041c 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in __ocfs2_flush_truncate_log
* Struck through repros no longer work on HEAD.