KASAN: use-after-free Read in ocfs2_claim_suballoc_bits

Status: auto-obsoleted due to no activity on 2026/04/12 00:51
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+7ee70fbe2ae94f89be13@syzkaller.appspotmail.com
First crash: 493d, last: 216d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2025/04/04 upstream (ToT) e48e99b6edf4 C [report] KASAN: use-after-free Read in ocfs2_claim_suballoc_bits
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 KASAN: use-after-free Read in ocfs2_claim_suballoc_bits origin:upstream missing-backport 19 syz, C inconclusive 5 224d 368d 0/2 upstream: reported C repro on 2025/08/03 18:38
upstream KASAN: use-after-free Read in ocfs2_claim_suballoc_bits ocfs2 19 syz, C inconclusive 326 241d 714d 29/29 fixed on 2026/01/07 12:29
linux-6.1 KASAN: use-after-free Read in ocfs2_claim_suballoc_bits origin:upstream missing-backport 19 syz, C inconclusive 5 217d 431d 0/3 upstream: reported C repro on 2025/06/01 03:41
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/04/12 00:32 17m retest repro linux-5.15.y OK log
2025/04/14 11:16 11m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (8)
Created Duration User Patch Repo Result
2026/02/01 00:06 2m bisect fix linux-5.15.y error job log
2026/01/01 22:00 1h44m bisect fix linux-5.15.y OK (0) job log log
2025/11/30 06:12 1h32m bisect fix linux-5.15.y OK (0) job log log
2025/10/29 06:17 6h09m bisect fix linux-5.15.y OK (0) job log log
2025/09/20 09:05 1h56m bisect fix linux-5.15.y OK (0) job log log
2025/08/16 00:18 2h22m bisect fix linux-5.15.y OK (0) job log log
2025/07/16 19:58 3h18m bisect fix linux-5.15.y OK (0) job log log
2025/05/16 05:07 1h33m bisect fix linux-5.15.y OK (0) job log log

Sample crash report:
loop0: detected capacity change from 0 to 32768
ocfs2: Slot 0 on device (7,0) was already allocated to this node!
ocfs2: Mounting device (7,0) on (node local, slot 0) with ordered data mode.
==================================================================
BUG: KASAN: use-after-free in ocfs2_find_victim_chain fs/ocfs2/suballoc.c:1391 [inline]
BUG: KASAN: use-after-free in ocfs2_claim_suballoc_bits+0xfb5/0x24b0 fs/ocfs2/suballoc.c:1927
Read of size 4 at addr ffff88806ea58000 by task syz-executor830/4168

CPU: 1 PID: 4168 Comm: syz-executor830 Not tainted 5.15.179-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 print_address_description+0x63/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0x16b/0x1c0 mm/kasan/report.c:451
 ocfs2_find_victim_chain fs/ocfs2/suballoc.c:1391 [inline]
 ocfs2_claim_suballoc_bits+0xfb5/0x24b0 fs/ocfs2/suballoc.c:1927
 __ocfs2_claim_clusters+0x327/0xa30 fs/ocfs2/suballoc.c:2338
 ocfs2_local_alloc_new_window fs/ocfs2/localalloc.c:1170 [inline]
 ocfs2_local_alloc_slide_window fs/ocfs2/localalloc.c:1299 [inline]
 ocfs2_reserve_local_alloc_bits+0x1411/0x27a0 fs/ocfs2/localalloc.c:668
 ocfs2_reserve_clusters_with_limit+0x1b4/0xb50 fs/ocfs2/suballoc.c:1162
 ocfs2_mknod+0x1535/0x2cd0 fs/ocfs2/namei.c:354
 ocfs2_mkdir+0x194/0x430 fs/ocfs2/namei.c:657
 vfs_mkdir+0x3b6/0x590 fs/namei.c:4065
 do_mkdirat+0x260/0x520 fs/namei.c:4090
 __do_sys_mkdirat fs/namei.c:4105 [inline]
 __se_sys_mkdirat fs/namei.c:4103 [inline]
 __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f94713cb129
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 21 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd77634438 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f94713cb129
RDX: 0000000000000000 RSI: 00002000000000c0 RDI: 00000000ffffff9c
RBP: 0000000000000004 R08: 0000000000004458 R09: 0000000000000000
R10: 00007ffd776344d0 R11: 0000000000000246 R12: 0000000001000000
R13: 00007ffd776344d0 R14: 0000200000000240 R15: 0000000000000003
 </TASK>

The buggy address belongs to the page:
page:ffffea0001ba9600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x6ea58
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001ba9648 ffffea0001ba95c8 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x1100cca(GFP_HIGHUSER_MOVABLE), pid 4163, ts 54889812237, free_ts 55378275758
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x3b78/0x3d40 mm/page_alloc.c:4192
 __alloc_pages+0x272/0x700 mm/page_alloc.c:5466
 alloc_pages_vma+0x39a/0x800 mm/mempolicy.c:2146
 shmem_alloc_page mm/shmem.c:1586 [inline]
 shmem_alloc_and_acct_page+0x4d1/0xd10 mm/shmem.c:1611
 shmem_getpage_gfp+0x17b1/0x3190 mm/shmem.c:1906
 shmem_getpage mm/shmem.c:151 [inline]
 shmem_write_begin+0xce/0x1a0 mm/shmem.c:2474
 generic_perform_write+0x2bf/0x5b0 mm/filemap.c:3785
 __generic_file_write_iter+0x243/0x4f0 mm/filemap.c:3912
 generic_file_write_iter+0xa7/0x1b0 mm/filemap.c:3944
 call_write_iter include/linux/fs.h:2172 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0xacd/0xe50 fs/read_write.c:594
 ksys_write+0x1a2/0x2c0 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0xc34/0xcf0 mm/page_alloc.c:3317
 free_unref_page_list+0x1f7/0x8e0 mm/page_alloc.c:3433
 release_pages+0x1bb9/0x1f40 mm/swap.c:963
 __pagevec_release+0x80/0xf0 mm/swap.c:983
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x67a/0x1b50 mm/shmem.c:964
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x21b/0xa00 mm/shmem.c:1145
 evict+0x529/0x930 fs/inode.c:647
 __dentry_kill+0x436/0x650 fs/dcache.c:586
 dentry_kill+0xbb/0x290 fs/dcache.c:-1
 dput+0xd8/0x1a0 fs/dcache.c:893
 __fput+0x636/0x8e0 fs/file_table.c:319
 task_work_run+0x129/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x106/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x5d/0x240 kernel/entry/common.c:307
 do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86

Memory state around the buggy address:
 ffff88806ea57f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806ea57f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806ea58000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88806ea58080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806ea58100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/03/31 10:58 linux-5.15.y 0c935c049b5c d3999433 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan KASAN: use-after-free Read in ocfs2_claim_suballoc_bits
2025/03/31 10:14 linux-5.15.y 0c935c049b5c d3999433 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in ocfs2_claim_suballoc_bits
2025/06/16 05:35 linux-5.15.y 1c700860e8bc 5f4b362d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in ocfs2_claim_suballoc_bits
* Struck through repros no longer work on HEAD.