syzbot


KASAN: use-after-free Read in __ocfs2_flush_truncate_log

Status: upstream: reported C repro on 2026/06/07 20:02
Reported-by: syzbot+94da2b9a99715122ce75@syzkaller.appspotmail.com
First crash: 18d, last: 3d01h
Bug presence (1)
Date Name Commit Repro Result
2026/06/15 upstream (ToT) 8cd9520d35a6 C Failed due to an error; will retry later
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 197d 635d 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 C error 3 69d 396d 0/3 upstream: reported C repro on 2025/05/25 11:09

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 ffff0000eb802ac0 by task syz-executor/4441

CPU: 0 PID: 4441 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/02/2026
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

The buggy address belongs to the physical page:
page:00000000ca48af30 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12b802
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffc0003ae00c8 fffffc0003b49c08 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000eb802980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000eb802a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000eb802a80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff0000eb802b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000eb802b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
(syz-executor,4441,0):ocfs2_read_blocks:239 ERROR: status = -12
(syz-executor,4441,0):_ocfs2_free_suballoc_bits:2489 ERROR: status = -12
(syz-executor,4441,0):_ocfs2_free_clusters:2583 ERROR: status = -12
(syz-executor,4441,0):ocfs2_replay_truncate_records:5976 ERROR: status = -12
(syz-executor,4441,0):__ocfs2_flush_truncate_log:6057 ERROR: status = -12
(syz-executor,4441,0):ocfs2_sync_fs:404 ERROR: status = -12
ocfs2: Unmounting device (7,0) on (node local)
ocfs2: Unmounting device (7,0) on (node local)
ocfs2: Unmounting device (7,0) on (node local)

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
* Struck through repros no longer work on HEAD.