KASAN: slab-use-after-free Read in ocfs2_fault

Status: upstream: reported C repro on 2025/09/17 19:37
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+7bf539c666eded139bd7@syzkaller.appspotmail.com
First crash: 326d, last: 228d
Fix bisection: the issue occurs on the latest tested release (bisect log)
Crash: KASAN: slab-use-after-free Read in ocfs2_fault (log)
Repro: C syz .config
  
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2025/12/24 linux-6.6.y (ToT) 5fa4793a2d2d C [report] KASAN: slab-use-after-free Read in ocfs2_fault
2025/09/20 upstream (ToT) cd89d487374c C [report] KASAN: slab-use-after-free Read in ocfs2_fault
2025/12/24 upstream (ToT) b927546677c8 C Didn't crash
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in ocfs2_fault ocfs2 19 syz, C done 363 117d 697d 29/29 fixed on 2026/05/21 07:50
linux-5.15 KASAN: use-after-free Read in ocfs2_fault 19 1 457d 457d 0/3 auto-obsoleted due to no activity on 2025/08/18 07:54
linux-6.1 KASAN: use-after-free Read in ocfs2_fault origin:lts-only 19 syz, C error 22 100d 436d 0/3 upstream: reported C repro on 2025/05/31 00:13
linux-5.15 KASAN: use-after-free Read in ocfs2_fault (2) origin:upstream 19 syz, C error 3 87d 207d 0/3 upstream: reported C repro on 2026/01/15 08:30
▶ ▼ Fix bisection attempts (6)
Created Duration User Patch Repo Result
2026/06/07 00:38 11m fix candidate upstream error job log
2026/03/27 07:16 0m fix candidate upstream error job log
2026/02/22 04:07 1m fix candidate upstream error job log
2026/01/23 00:24 1m fix candidate upstream error job log
2025/11/24 23:02 2h00m bisect fix linux-6.6.y OK (0) job log log
2025/10/25 03:56 2h09m bisect fix linux-6.6.y OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in ocfs2_fault+0xd7/0x3d0 fs/ocfs2/mmap.c:41
Read of size 8 at addr ffff888077010d88 by task syz.3.29/6065

CPU: 0 PID: 6065 Comm: syz.3.29 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x220 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 ocfs2_fault+0xd7/0x3d0 fs/ocfs2/mmap.c:41
 __do_fault+0x13b/0x4e0 mm/memory.c:4243
 do_read_fault mm/memory.c:4616 [inline]
 do_fault mm/memory.c:4753 [inline]
 do_pte_missing mm/memory.c:3688 [inline]
 handle_pte_fault mm/memory.c:5025 [inline]
 __handle_mm_fault mm/memory.c:5166 [inline]
 handle_mm_fault+0x3886/0x4920 mm/memory.c:5331
 faultin_page mm/gup.c:868 [inline]
 __get_user_pages+0x5ea/0x1470 mm/gup.c:1167
 populate_vma_page_range+0x2b6/0x370 mm/gup.c:1593
 __mm_populate+0x24c/0x380 mm/gup.c:1696
 mm_populate include/linux/mm.h:3328 [inline]
 vm_mmap_pgoff+0x2e7/0x400 mm/util.c:561
 ksys_mmap_pgoff+0x520/0x700 mm/mmap.c:1431
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7faa7418eba9
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:00007faa74fb4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007faa743d5fa0 RCX: 00007faa7418eba9
RDX: 00000000027ffff7 RSI: 0000000000600000 RDI: 0000200000000000
RBP: 00007faa74211e19 R08: 0000000000000004 R09: 0000000000000000
R10: 0000000004012011 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faa743d6038 R14: 00007faa743d5fa0 R15: 00007ffed3d1b8e8
 </TASK>

Allocated by task 6065:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3519
 vm_area_alloc+0x24/0x1d0 kernel/fork.c:486
 __mmap_region mm/mmap.c:2770 [inline]
 mmap_region+0xc8a/0x2020 mm/mmap.c:2941
 do_mmap+0x92f/0x10a0 mm/mmap.c:1385
 vm_mmap_pgoff+0x1c0/0x400 mm/util.c:556
 ksys_mmap_pgoff+0x520/0x700 mm/mmap.c:1431
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 16:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 kmem_cache_free+0xf8/0x280 mm/slub.c:3852
 rcu_do_batch kernel/rcu/tree.c:2194 [inline]
 rcu_core+0xcc4/0x1720 kernel/rcu/tree.c:2467
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 run_ksoftirqd+0x9c/0xf0 kernel/softirq.c:950
 smpboot_thread_fn+0x635/0xa00 kernel/smpboot.c:164
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x158/0x930 kernel/rcu/tree.c:2837
 remove_vma mm/mmap.c:148 [inline]
 remove_mt mm/mmap.c:2323 [inline]
 do_vmi_align_munmap+0x1403/0x1660 mm/mmap.c:2596
 do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2660
 __vm_munmap+0x193/0x3c0 mm/mmap.c:2961
 __do_sys_munmap mm/mmap.c:2978 [inline]
 __se_sys_munmap mm/mmap.c:2975 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:2975
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888077010d00
 which belongs to the cache vm_area_struct of size 192
The buggy address is located 136 bytes inside of
 freed 192-byte region [ffff888077010d00, ffff888077010dc0)

The buggy address belongs to the physical page:
page:ffffea0001dc0400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x77010
memcg:ffff88807f36e801
flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff888019a4cb40 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000001ffffffff ffff88807f36e801
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 5947, tgid 5947 (udevd), ts 114448487869, free_ts 113625430157
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 alloc_slab_page+0x5d/0x170 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2e0 mm/slub.c:2081
 ___slab_alloc+0xc6d/0x1300 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x1b7/0x2e0 mm/slub.c:3519
 vm_area_dup+0x27/0x270 kernel/fork.c:501
 __split_vma+0x19f/0xc00 mm/mmap.c:2373
 do_vmi_align_munmap+0x377/0x1660 mm/mmap.c:2514
 do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2660
 __vm_munmap+0x193/0x3c0 mm/mmap.c:2961
 __do_sys_munmap mm/mmap.c:2978 [inline]
 __se_sys_munmap mm/mmap.c:2975 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:2975
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
 release_pages+0x1fa0/0x2220 mm/swap.c:1022
 __folio_batch_release+0x71/0xe0 mm/swap.c:1042
 folio_batch_release include/linux/pagevec.h:83 [inline]
 truncate_inode_pages_range+0x358/0xf00 mm/truncate.c:371
 kill_bdev block/bdev.c:76 [inline]
 blkdev_flush_mapping+0x132/0x290 block/bdev.c:632
 blkdev_put_whole block/bdev.c:663 [inline]
 blkdev_put+0x498/0x760 block/bdev.c:941
 blkdev_release+0x84/0x90 block/fops.c:604
 __fput+0x234/0x970 fs/file_table.c:384
 __do_sys_close fs/open.c:1571 [inline]
 __se_sys_close+0x15f/0x220 fs/open.c:1556
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff888077010c80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
 ffff888077010d00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888077010d80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                      ^
 ffff888077010e00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888077010e80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/17 21:04 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ocfs2_fault
2025/12/24 17:21 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ocfs2_fault
2025/09/17 19:36 linux-6.6.y 60a9e718726f e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in ocfs2_fault
* Struck through repros no longer work on HEAD.