KASAN: use-after-free Read in __ocfs2_flush_truncate_log

Status: upstream: reported C repro on 2025/05/25 11:09
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+53be1be98c6397911454@syzkaller.appspotmail.com
First crash: 428d, last: 23d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/05/27 linux-5.15.y (ToT) 98f47d0e9b8c C [report] KASAN: slab-out-of-bounds Read in __ocfs2_flush_truncate_log
2025/05/27 upstream (ToT) 015a99fa7665 C Didn't crash
▶ ▼ Similar bugs (2)
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 C inconclusive inconclusive 41 229d 667d 0/29 auto-obsoleted due to no activity on 2026/06/12 00:20
linux-6.1 KASAN: use-after-free Read in __ocfs2_flush_truncate_log 19 C 4 5d23h 50d 0/3 upstream: reported C repro on 2026/06/07 20:02
▶ ▼ Last patch testing requests (5)
Created Duration User Patch Repo Result
2026/07/04 17:37 18m retest repro linux-5.15.y report log
2026/04/17 22:25 11m retest repro linux-5.15.y report log
2026/02/06 20:58 11m retest repro linux-5.15.y report log
2025/11/28 09:50 11m retest repro linux-5.15.y report log
2025/09/18 08:15 1h05m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (8)
Created Duration User Patch Repo Result
2026/05/10 15:36 19m fix candidate upstream error job log
2026/03/25 19:06 1m fix candidate upstream error job log
2026/02/23 09:32 1m fix candidate upstream error job log
2026/01/23 13:03 1m fix candidate upstream error job log
2025/11/13 14:19 1m fix candidate upstream error job log
2025/08/19 18:32 4m fix candidate upstream error job log
2025/07/16 15:41 1m fix candidate upstream error job log
2025/07/01 05:53 1m bisect fix linux-5.15.y error job log

Sample crash report:
=======================================================
ocfs2: Mounting device (7,0) on (node local, slot 0) with ordered data mode.
==================================================================
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+0x64c/0xf30 fs/ocfs2/alloc.c:6053
Read of size 4 at addr ffff0000e2af7ab8 by task syz-executor132/4023

CPU: 1 PID: 4023 Comm: syz-executor132 Not tainted 5.15.184-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x78/0x30c mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xec/0x15c mm/kasan/report.c:451
 __asan_report_load4_noabort+0x44/0x50 mm/kasan/report_generic.c:308
 ocfs2_replay_truncate_records fs/ocfs2/alloc.c:5959 [inline]
 __ocfs2_flush_truncate_log+0x64c/0xf30 fs/ocfs2/alloc.c:6053
 ocfs2_flush_truncate_log+0x48/0x68 fs/ocfs2/alloc.c:6075
 ocfs2_sync_fs+0xf8/0x2a4 fs/ocfs2/super.c:403
 sync_filesystem+0x1a0/0x218 fs/sync.c:66
 generic_shutdown_super+0x70/0x2f0 fs/super.c:448
 kill_block_super+0x70/0xdc fs/super.c:1427
 deactivate_locked_super+0xb8/0x13c fs/super.c:335
 deactivate_super+0xf8/0x118 fs/super.c:366
 cleanup_mnt+0x3a4/0x458 fs/namespace.c:1143
 __cleanup_mnt+0x20/0x30 fs/namespace.c:1150
 task_work_run+0x12c/0x1e0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x67c/0x1f58 kernel/exit.c:874
 do_group_exit+0x100/0x268 kernel/exit.c:996
 __do_sys_exit_group kernel/exit.c:1007 [inline]
 __se_sys_exit_group kernel/exit.c:1005 [inline]
 __wake_up_parent+0x0/0x60 kernel/exit.c:1005
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

The buggy address belongs to the page:
page:00000000c0228cea refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x122af7
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffc00038abdc8 fffffc00038abdc8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000e2af7980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e2af7a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000e2af7a80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                        ^
 ffff0000e2af7b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e2af7b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
------------[ cut here ]------------
kernel BUG at fs/ocfs2/suballoc.c:2469!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4023 Comm: syz-executor132 Tainted: G    B             5.15.184-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : _ocfs2_free_suballoc_bits+0xc50/0xf70 fs/ocfs2/suballoc.c:2469
lr : _ocfs2_free_suballoc_bits+0xc50/0xf70 fs/ocfs2/suballoc.c:2469
sp : ffff80001cfb73c0
x29: ffff80001cfb7520 x28: 00000000fb11ff4a x27: dfff800000000000
x26: ffff0000e3153478 x25: ffff800009cdfafc x24: ffff0000e2a74e00
x23: ffff7000039f6e88 x22: 0000000000000e00 x21: 0000000000000e00
x20: 000000000f90c000 x19: 00000000fb1203e1 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000111a5644 x15: 00000000fffffffc
x14: 0000000000ff0100 x13: ffffffffffffffff x12: 0000000000ff0100
x11: 0000000000000000 x10: 0000000000000000 x9 : ffff800009ce5208
x8 : ffff0000d79cb680 x7 : 0000000000000000 x6 : ffff800009cdfafc
x5 : 00000000fb11ff4a x4 : 000000000f90c000 x3 : 0000000000000497
x2 : ffff0000dd3cb0e8 x1 : 0000000000000e00 x0 : 00000000fb1203e1
Call trace:
 _ocfs2_free_suballoc_bits+0xc50/0xf70 fs/ocfs2/suballoc.c:2469
 _ocfs2_free_clusters+0x510/0x9b0 fs/ocfs2/suballoc.c:2569
 ocfs2_free_clusters+0x50/0x68 fs/ocfs2/suballoc.c:2590
 ocfs2_replay_truncate_records fs/ocfs2/alloc.c:5971 [inline]
 __ocfs2_flush_truncate_log+0x5b0/0xf30 fs/ocfs2/alloc.c:6053
 ocfs2_flush_truncate_log+0x48/0x68 fs/ocfs2/alloc.c:6075
 ocfs2_sync_fs+0xf8/0x2a4 fs/ocfs2/super.c:403
 sync_filesystem+0x1a0/0x218 fs/sync.c:66
 generic_shutdown_super+0x70/0x2f0 fs/super.c:448
 kill_block_super+0x70/0xdc fs/super.c:1427
 deactivate_locked_super+0xb8/0x13c fs/super.c:335
 deactivate_super+0xf8/0x118 fs/super.c:366
 cleanup_mnt+0x3a4/0x458 fs/namespace.c:1143
 __cleanup_mnt+0x20/0x30 fs/namespace.c:1150
 task_work_run+0x12c/0x1e0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x67c/0x1f58 kernel/exit.c:874
 do_group_exit+0x100/0x268 kernel/exit.c:996
 __do_sys_exit_group kernel/exit.c:1007 [inline]
 __se_sys_exit_group kernel/exit.c:1005 [inline]
 __wake_up_parent+0x0/0x60 kernel/exit.c:1005
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
Code: 17fffec8 979e4dc1 d4210000 979e4dbf (d4210000) 
---[ end trace 4327436f4ad1c157 ]---

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/25 11:09 linux-5.15.y 98f47d0e9b8c ed351ea7 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2025/07/28 05:07 linux-5.15.y c79648372d02 fb8f743d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in __ocfs2_flush_truncate_log
2025/06/01 00:03 linux-5.15.y 98f47d0e9b8c 3d2f584d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in __ocfs2_flush_truncate_log
* Struck through repros no longer work on HEAD.