KASAN: use-after-free Read in ocfs2_dir_foreach_blk

Status: upstream: reported C repro on 2025/02/03 04:13
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+207f6ce08909b626016f@syzkaller.appspotmail.com
First crash: 543d, last: 211d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2026/01/01 linux-6.1.y (ToT) 50cbba13faa2 C [report] KASAN: out-of-bounds Read in ocfs2_dir_foreach_blk
2025/03/23 upstream (ToT) 586de92313fc C [report] KASAN: use-after-free Read in ocfs2_dir_foreach_blk
2026/01/01 upstream (ToT) b69053dd3ffb 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_dir_foreach_blk ocfs2 19 syz, C error 115 231d 672d 29/29 fixed on 2026/01/07 12:29
linux-5.15 KASAN: use-after-free Read in ocfs2_dir_foreach_blk origin:upstream 19 syz, C error 4 17h15m 317d 0/3 upstream: reported C repro on 2025/09/17 13:54
▶ ▼ Fix bisection attempts (12)
Created Duration User Patch Repo Result
2026/06/09 19:12 15m fix candidate upstream error job log
2026/03/25 13:46 3m fix candidate upstream error job log
2026/02/22 04:03 1m fix candidate upstream error job log
2026/01/22 14:08 3m fix candidate upstream error job log
2025/11/20 06:34 0m bisect fix linux-6.1.y error job log
2025/10/20 09:23 2h10m bisect fix linux-6.1.y OK (0) job log log
2025/09/15 07:27 1h22m bisect fix linux-6.1.y OK (0) job log log
2025/08/08 12:10 1h55m bisect fix linux-6.1.y OK (0) job log log
2025/07/07 20:30 1h45m bisect fix linux-6.1.y OK (0) job log log
2025/06/07 07:19 1h43m bisect fix linux-6.1.y OK (0) job log log
2025/04/10 00:41 2h19m bisect fix linux-6.1.y OK (0) job log log
2025/03/05 18:26 2h09m bisect fix linux-6.1.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 ordered 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+0x1600/0x1990 fs/ocfs2/dir.c:1927
Read of size 2 at addr ffff88805af848c9 by task syz.0.24/4457

CPU: 1 PID: 4457 Comm: syz.0.24 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 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+0x1600/0x1990 fs/ocfs2/dir.c:1927
 ocfs2_readdir+0x237/0x4f0 fs/ocfs2/dir.c:1970
 iterate_dir+0x218/0x560 fs/readdir.c:-1
 __do_sys_getdents64 fs/readdir.c:369 [inline]
 __se_sys_getdents64+0xe5/0x260 fs/readdir.c:354
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb9c438f749
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:00007ffff7702e28 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007fb9c45e5fa0 RCX: 00007fb9c438f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007fb9c4413f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb9c45e5fa0 R14: 00007fb9c45e5fa0 R15: 0000000000000003
 </TASK>

The buggy address belongs to the physical page:
page:ffffea00016be100 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5af84
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea00016be148 ffffea00016be0c8 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 4354, tgid 4354 (udevd), ts 101420670675, free_ts 101470018012
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x1a26/0x1ac0 mm/page_alloc.c:4328
 __alloc_pages+0x1df/0x4e0 mm/page_alloc.c:5614
 __folio_alloc+0xe/0x30 mm/page_alloc.c:5646
 vma_alloc_folio+0x4a3/0x900 mm/mempolicy.c:2243
 alloc_page_vma include/linux/gfp.h:284 [inline]
 do_anonymous_page mm/memory.c:4191 [inline]
 handle_pte_fault mm/memory.c:5029 [inline]
 __handle_mm_fault mm/memory.c:5173 [inline]
 handle_mm_fault+0x2237/0x3e60 mm/memory.c:5294
 do_user_addr_fault+0x51f/0xb10 arch/x86/mm/fault.c:1340
 handle_page_fault arch/x86/mm/fault.c:1431 [inline]
 exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1487
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:608
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page_list+0xbb/0x8e0 mm/page_alloc.c:3525
 release_pages+0x1f92/0x2200 mm/swap.c:1035
 tlb_batch_pages_flush mm/mmu_gather.c:59 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:254 [inline]
 tlb_flush_mmu+0xff/0x210 mm/mmu_gather.c:261
 tlb_finish_mmu+0xbd/0x1c0 mm/mmu_gather.c:361
 unmap_region+0x272/0x2c0 mm/mmap.c:2343
 do_mas_align_munmap+0xc57/0x1220 mm/mmap.c:2592
 do_mas_munmap+0x240/0x2b0 mm/mmap.c:2650
 __vm_munmap+0x18d/0x290 mm/mmap.c:2936
 __do_sys_munmap mm/mmap.c:2961 [inline]
 __se_sys_munmap mm/mmap.c:2958 [inline]
 __x64_sys_munmap+0x5c/0x70 mm/mmap.c:2958
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88805af84780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805af84800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805af84880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88805af84900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805af84980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/24 09:51 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-6-1-kasan KASAN: use-after-free Read in ocfs2_dir_foreach_blk
2025/02/03 05:13 linux-6.1.y 0cbb5f65e52f 568559e4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-1-kasan KASAN: use-after-free Read in ocfs2_dir_foreach_blk
2025/02/03 04:38 linux-6.1.y 0cbb5f65e52f 568559e4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-1-kasan KASAN: use-after-free Read in ocfs2_dir_foreach_blk
2025/12/24 09:00 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in ocfs2_dir_foreach_blk
2025/02/03 04:12 linux-6.1.y 0cbb5f65e52f 568559e4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in ocfs2_dir_foreach_blk
2025/05/07 12:39 linux-6.1.y ac7079a42ea5 350f4ffc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in ocfs2_dir_foreach_blk
* Struck through repros no longer work on HEAD.