KASAN: use-after-free Read in ocfs2_dir_foreach_blk

Status: upstream: reported C repro on 2025/09/17 13:54
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+7594196c6b2e25ddda51@syzkaller.appspotmail.com
First crash: 316d, last: 15d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2025/09/21 upstream (ToT) f975f08c2e89 C [report] KASAN: use-after-free Read in ocfs2_dir_foreach_blk
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in ocfs2_dir_foreach_blk ocfs2 19 syz, C error 115 230d 671d 29/29 fixed on 2026/01/07 12:29
linux-6.1 KASAN: use-after-free Read in ocfs2_dir_foreach_blk origin:upstream missing-backport 19 syz, C error 6 210d 542d 0/3 upstream: reported C repro on 2025/02/03 04:13
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/07/14 16:22 1h27m retest repro linux-5.15.y report log
2026/05/14 19:14 15m retest repro linux-5.15.y report log
2026/05/14 19:14 15m retest repro linux-5.15.y report log
2026/04/23 13:19 16m retest repro linux-5.15.y report log
2026/02/19 09:51 38m retest repro linux-5.15.y report log
2026/02/19 09:51 41m retest repro linux-5.15.y report log
2025/12/11 00:06 14m retest repro linux-5.15.y report log
2025/12/11 00:06 14m retest repro linux-5.15.y report log
2025/10/01 20:45 12m retest repro linux-5.15.y report log
2025/10/01 20:45 12m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2026/02/12 03:17 0m bisect fix linux-5.15.y error job log
2026/01/13 00:29 2h46m bisect fix linux-5.15.y OK (0) job log log
2025/11/09 05:32 1h49m bisect fix linux-5.15.y OK (0) job log log

Sample crash report:
loop0: detected capacity change from 0 to 32768
ocfs2: Mounting device (7,0) on (node local, slot 0) with writeback data mode.
==================================================================
BUG: KASAN: use-after-free in ocfs2_check_dir_entry fs/ocfs2/dir.c:305 [inline]
BUG: KASAN: use-after-free in ocfs2_dir_foreach_blk_id fs/ocfs2/dir.c:1799 [inline]
BUG: KASAN: use-after-free in ocfs2_dir_foreach_blk+0x1566/0x1900 fs/ocfs2/dir.c:1927
Read of size 2 at addr ffff88805a5adcf0 by task syz.0.32/4404

CPU: 0 PID: 4404 Comm: syz.0.32 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 ocfs2_check_dir_entry fs/ocfs2/dir.c:305 [inline]
 ocfs2_dir_foreach_blk_id fs/ocfs2/dir.c:1799 [inline]
 ocfs2_dir_foreach_blk+0x1566/0x1900 fs/ocfs2/dir.c:1927
 ocfs2_readdir+0x21a/0x460 fs/ocfs2/dir.c:1970
 iterate_dir+0x218/0x560 fs/readdir.c:-1
 __do_sys_getdents fs/readdir.c:286 [inline]
 __se_sys_getdents+0xe5/0x250 fs/readdir.c:271
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f28d65efba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcf0c74cf8 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f28d6836fa0 RCX: 00007f28d65efba9
RDX: 0000000000000054 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f28d6672e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f28d6836fa0 R14: 00007f28d6836fa0 R15: 0000000000000003
 </TASK>

The buggy address belongs to the page:
page:ffffea0001696b40 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5a5ad
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001696b88 ffffea0001696b08 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 4389, ts 89870589030, free_ts 90195377784
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
 __alloc_pages+0x1e1/0x470 mm/page_alloc.c:5487
 alloc_pages_vma+0x393/0x7c0 mm/mempolicy.c:2146
 shmem_alloc_page mm/shmem.c:1586 [inline]
 shmem_alloc_and_acct_page+0x427/0xb70 mm/shmem.c:1611
 shmem_getpage_gfp+0x14f4/0x2d40 mm/shmem.c:1906
 shmem_getpage mm/shmem.c:151 [inline]
 shmem_write_begin+0xcd/0x1a0 mm/shmem.c:2474
 generic_perform_write+0x2aa/0x530 mm/filemap.c:3785
 __generic_file_write_iter+0x25f/0x4e0 mm/filemap.c:3912
 generic_file_write_iter+0xa6/0x1b0 mm/filemap.c:3944
 call_write_iter include/linux/fs.h:2172 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x712/0xd00 fs/read_write.c:594
 ksys_write+0x14d/0x250 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 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+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page_list+0x122/0x7e0 mm/page_alloc.c:3433
 release_pages+0x184b/0x1bb0 mm/swap.c:963
 __pagevec_release+0x6d/0xe0 mm/swap.c:983
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x5cb/0x1880 mm/shmem.c:964
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x20d/0xa00 mm/shmem.c:1145
 evict+0x485/0x870 fs/inode.c:647
 __dentry_kill+0x431/0x650 fs/dcache.c:586
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xd8/0x1a0 fs/dcache.c:893
 __fput+0x5ee/0x930 fs/file_table.c:319
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86

Memory state around the buggy address:
 ffff88805a5adb80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805a5adc00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805a5adc80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff88805a5add00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805a5add80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/17 17:45 linux-5.15.y 43bb85222e53 e2beed91 .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_dir_foreach_blk
2025/09/17 15:51 linux-5.15.y 43bb85222e53 e2beed91 .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_dir_foreach_blk
2025/09/17 14:54 linux-5.15.y 43bb85222e53 e2beed91 .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_dir_foreach_blk
2025/09/17 13:53 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in ocfs2_dir_foreach_blk
* Struck through repros no longer work on HEAD.