KASAN: slab-use-after-free Read in lru_add (2)

Status: upstream: reported C repro on 2025/08/04 16:51
Subsystems: gfs2 mm
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+8921d5debffa05b33b27@syzkaller.appspotmail.com
First crash: 373d, last: 95d
Cause bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
81a43dc7 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in lru_add (2) 2026/05/31 18:25 2026/05/31 18:25 2026/05/31 19:29 6b4a8443
ac8a2cdc assessment-security 💥 KASAN: slab-use-after-free Read in lru_add (2) 2026/05/15 06:08 2026/05/15 06:08 2026/05/15 06:10 6ccb967e
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] gfs2: validate metadata block numbers before reading them 1 (1) 2026/07/15 12:06
[syzbot] [mm?] [gfs2?] KASAN: slab-use-after-free Read in lru_add (2) 0 (1) 2025/08/04 16:51
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in lru_add mm 19 1 621d 616d 0/29 auto-obsoleted due to no activity on 2025/03/10 08:33
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/07/21 05:31 1h01m retest repro linux-next error
2026/07/21 04:57 51m retest repro linux-next error
2026/07/21 04:57 31m retest repro linux-next error
2026/06/16 21:28 32m retest repro linux-next log
2026/05/10 00:52 37m retest repro linux-next report log
2026/05/10 00:52 38m retest repro linux-next report log
2026/04/07 09:50 17m retest repro linux-next report log
2026/01/27 08:09 50m retest repro linux-next report log
2025/10/27 17:17 43m retest repro linux-next report log
2025/08/18 16:02 28m retest repro linux-next report log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:82 [inline]
BUG: KASAN: slab-use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: slab-use-after-free in mapping_unevictable include/linux/pagemap.h:269 [inline]
BUG: KASAN: slab-use-after-free in folio_evictable mm/internal.h:584 [inline]
BUG: KASAN: slab-use-after-free in lru_add+0x265/0xee0 mm/swap.c:136
Read of size 8 at addr ffff888021afd520 by task udevd/5837

CPU: 0 UID: 0 PID: 5837 Comm: udevd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
 instrument_atomic_read include/linux/instrumented.h:82 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 mapping_unevictable include/linux/pagemap.h:269 [inline]
 folio_evictable mm/internal.h:584 [inline]
 lru_add+0x265/0xee0 mm/swap.c:136
 folio_batch_move_lru+0x336/0x550 mm/swap.c:172
 lru_add_drain_cpu+0xb4/0x770 mm/swap.c:654
 lru_add_drain+0x142/0x3f0 mm/swap.c:743
 __folio_batch_release+0x48/0x90 mm/swap.c:1065
 folio_batch_release include/linux/folio_batch.h:101 [inline]
 shmem_undo_range+0x52c/0x1660 mm/shmem.c:1149
 shmem_truncate_range mm/shmem.c:1277 [inline]
 shmem_evict_inode+0x289/0xae0 mm/shmem.c:1407
 evict+0x61e/0xb10 fs/inode.c:841
 __dentry_kill+0x1a2/0x690 fs/dcache.c:718
 finish_dput+0xc9/0x480 fs/dcache.c:927
 end_renaming fs/namei.c:4124 [inline]
 filename_renameat2+0x61e/0x9c0 fs/namei.c:6174
 __do_sys_rename fs/namei.c:6216 [inline]
 __se_sys_rename+0x55/0x2c0 fs/namei.c:6212
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4617f67cc7
Code: e8 5e a7 09 00 f7 d8 19 c0 5b c3 0f 1f 84 00 00 00 00 00 b8 ff ff ff ff 5b c3 66 0f 1f 84 00 00 00 00 00 b8 52 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 01 61 17 00 f7 d8 64 89 02 b8
RSP: 002b:00007fff17580fc8 EFLAGS: 00000206 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 000055bd034710d0 RCX: 00007f4617f67cc7
RDX: 000055bd0344f010 RSI: 00007fff17580fe0 RDI: 00007fff175813e0
RBP: 000055bd03596000 R08: 00000000000001e0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007fff17580fe0
R13: 00007fff175813e0 R14: 0000000000000000 R15: 000055bccc0c59dd
 </TASK>

Allocated by task 6173:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 kmem_cache_alloc_noprof+0x33b/0x680 mm/slub.c:4905
 gfs2_glock_get+0x27b/0xf50 fs/gfs2/glock.c:1098
 gfs2_inode_lookup+0x29f/0xc50 fs/gfs2/inode.c:149
 gfs2_dir_search+0x168/0x220 fs/gfs2/dir.c:1665
 gfs2_lookupi+0x45e/0x640 fs/gfs2/inode.c:354
 gfs2_jindex_hold fs/gfs2/ops_fstype.c:573 [inline]
 init_journal+0x592/0x2280 fs/gfs2/ops_fstype.c:713
 init_inodes+0xdb/0x320 fs/gfs2/ops_fstype.c:844
 gfs2_fill_super+0x1a92/0x2220 fs/gfs2/ops_fstype.c:1250
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
 gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1332
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3834
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4360
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 29:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2689 [inline]
 slab_free mm/slub.c:6246 [inline]
 kmem_cache_free+0x187/0x6c0 mm/slub.c:6373
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core kernel/rcu/tree.c:2869 [inline]
 rcu_cpu_kthread+0x99e/0x1470 kernel/rcu/tree.c:2957
 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:57
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 __call_rcu_common kernel/rcu/tree.c:3131 [inline]
 call_rcu+0xee/0x890 kernel/rcu/tree.c:3251
 gfs2_glock_free+0x3c/0xa0 fs/gfs2/glock.c:152
 gfs2_glock_put_eventually fs/gfs2/super.c:1173 [inline]
 gfs2_evict_inode+0xe50/0x1430 fs/gfs2/super.c:1510
 evict+0x61e/0xb10 fs/inode.c:841
 gfs2_jindex_free+0x3a4/0x450 fs/gfs2/super.c:79
 init_journal+0x8aa/0x2280 fs/gfs2/ops_fstype.c:826
 init_inodes+0xdb/0x320 fs/gfs2/ops_fstype.c:844
 gfs2_fill_super+0x1a92/0x2220 fs/gfs2/ops_fstype.c:1250
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
 gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1332
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3834
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4360
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:57
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 insert_work+0x3d/0x330 kernel/workqueue.c:2226
 __queue_work+0xcfd/0x1010 kernel/workqueue.c:2381
 queue_delayed_work_on+0x11a/0x1e0 kernel/workqueue.c:2600
 queue_delayed_work include/linux/workqueue.h:711 [inline]
 gfs2_glock_queue_work fs/gfs2/glock.c:224 [inline]
 do_xmote+0x51b/0x760 fs/gfs2/glock.c:745
 glock_work_func+0x2a8/0x580 fs/gfs2/glock.c:1011
 process_one_work+0x9a3/0x1710 kernel/workqueue.c:3312
 process_scheduled_works kernel/workqueue.c:3403 [inline]
 worker_thread+0xba8/0x11e0 kernel/workqueue.c:3489
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888021afd0f0
 which belongs to the cache gfs2_glock(aspace) of size 1352
The buggy address is located 1072 bytes inside of
 freed 1352-byte region [ffff888021afd0f0, ffff888021afd638)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888021afdc80 pfn:0x21af8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000240(workingset|head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000240 ffff88801f304780 ffff88801f3fd288 ffff88801f3fd288
raw: ffff888021afdc80 0000000800160010 00000000f5000000 0000000000000000
head: 0080000000000240 ffff88801f304780 ffff88801f3fd288 ffff88801f3fd288
head: ffff888021afdc80 0000000800160010 00000000f5000000 0000000000000000
head: 0080000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6167, tgid 6167 (syz.0.23), ts 139830167183, free_ts 139791399184
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x27d6/0x2850 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3467
 new_slab mm/slub.c:3525 [inline]
 refill_objects+0x33c/0x3d0 mm/slub.c:7251
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x373/0x720 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 kmem_cache_alloc_noprof+0x433/0x680 mm/slub.c:4905
 gfs2_glock_get+0x27b/0xf50 fs/gfs2/glock.c:1098
 gfs2_inode_lookup+0x29f/0xc50 fs/gfs2/inode.c:149
 gfs2_dir_search+0x168/0x220 fs/gfs2/dir.c:1665
 gfs2_lookupi+0x45e/0x640 fs/gfs2/inode.c:354
 gfs2_jindex_hold fs/gfs2/ops_fstype.c:573 [inline]
 init_journal+0x592/0x2280 fs/gfs2/ops_fstype.c:713
 init_inodes+0xdb/0x320 fs/gfs2/ops_fstype.c:844
 gfs2_fill_super+0x1a92/0x2220 fs/gfs2/ops_fstype.c:1250
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
 gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1332
page last free pid 5837 tgid 5837 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0xf9b/0x10f0 mm/page_alloc.c:2943
 __slab_free+0x252/0x2a0 mm/slub.c:5608
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 __do_kmalloc_node mm/slub.c:5294 [inline]
 __kmalloc_noprof+0x399/0x7b0 mm/slub.c:5307
 kmalloc_noprof include/linux/slab.h:954 [inline]
 tomoyo_realpath_from_path+0xe3/0x5d0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_number_perm+0x246/0x630 security/tomoyo/file.c:728
 security_file_ioctl+0xc3/0x2a0 security/security.c:2512
 __do_sys_ioctl fs/ioctl.c:591 [inline]
 __se_sys_ioctl+0x47/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888021afd400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888021afd480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888021afd500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888021afd580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888021afd600: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/25 23:42 linux-next 7080e32d3f09 9c2d0995 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2026/04/24 07:09 linux-next 4c406406070d 9cfb3ca7 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2025/08/04 15:57 linux-next 5c5a10f0be96 7368264b .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2026/01/13 07:56 linux-next 0f853ca2a798 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2026/01/13 07:56 linux-next 0f853ca2a798 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2026/01/13 05:04 linux-next f417b7ffcbef d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2026/01/05 07:22 linux-next f8f97927abf7 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2026/01/02 05:46 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2025/12/29 17:47 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2025/12/28 19:15 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2025/12/25 05:42 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
2025/09/07 22:42 linux-next be5d4872e528 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in lru_add
* Struck through repros no longer work on HEAD.