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KASAN: use-after-free Read in slot_put

Status: upstream: reported on 2026/01/30 01:28
Reported-by: syzbot+9274a0e7ba218ea02417@syzkaller.appspotmail.com
First crash: 95d, last: 11d
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: null-ptr-deref Write in slot_put 12 1 259d 259d 0/3 auto-obsoleted due to no activity on 2025/11/26 13:38

Sample crash report:
RSP: 002b:00007ffd8de4e318 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fa8a5ec6048 RCX: 00007fa8a5e31a57
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffd8de4e3d0
RBP: 00007ffd8de4e3d0 R08: 00007ffd8de4f3d0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd8de4f460
R13: 00007fa8a5ec6048 R14: 0000000000029d71 R15: 00007ffd8de4f4a0
 </TASK>
==================================================================
BUG: KASAN: use-after-free in slot_put+0x16f/0x1e0 fs/gfs2/quota.c:357
Read of size 4 at addr ffff8880550a20ac by task syz-executor/6373

CPU: 0 PID: 6373 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 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
 slot_put+0x16f/0x1e0 fs/gfs2/quota.c:357
 qd_unlock+0x189/0x2d0 fs/gfs2/quota.c:501
 gfs2_quota_sync+0x5cf/0x700 fs/gfs2/quota.c:1336
 gfs2_sync_fs+0x48/0xb0 fs/gfs2/super.c:651
 sync_filesystem+0xe6/0x220 fs/sync.c:56
 generic_shutdown_super+0x6b/0x300 fs/super.c:448
 kill_block_super+0x7c/0xe0 fs/super.c:1427
 deactivate_locked_super+0x93/0xf0 fs/super.c:335
 cleanup_mnt+0x42d/0x4e0 fs/namespace.c:1148
 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
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa8a5e31a57
Code: a2 c7 05 9c fc 24 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffd8de4e318 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fa8a5ec6048 RCX: 00007fa8a5e31a57
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffd8de4e3d0
RBP: 00007ffd8de4e3d0 R08: 00007ffd8de4f3d0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd8de4f460
R13: 00007fa8a5ec6048 R14: 0000000000029d71 R15: 00007ffd8de4f4a0
 </TASK>

Allocated by task 6493:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 __kasan_slab_alloc+0x9c/0xd0 mm/kasan/common.c:467
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x100/0x290 mm/slub.c:3238
 kmem_cache_zalloc include/linux/slab.h:728 [inline]
 qd_alloc+0x50/0x260 fs/gfs2/quota.c:216
 gfs2_quota_init+0x74e/0xea0 fs/gfs2/quota.c:1426
 gfs2_make_fs_rw+0x414/0x580 fs/gfs2/super.c:159
 gfs2_fill_super+0x1837/0x1f00 fs/gfs2/ops_fstype.c:1276
 get_tree_bdev+0x3f1/0x610 fs/super.c:1325
 gfs2_get_tree+0x4d/0x1e0 fs/gfs2/ops_fstype.c:1332
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x24a/0xa40 fs/namespace.c:3034
 do_mount fs/namespace.c:3377 [inline]
 __do_sys_mount fs/namespace.c:3585 [inline]
 __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3562
 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

Freed by task 6373:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kmem_cache_free+0x8f/0x210 mm/slub.c:3520
 rcu_do_batch kernel/rcu/tree.c:2523 [inline]
 rcu_core+0x9d2/0x1670 kernel/rcu/tree.c:2763
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676

Last potentially related work creation:
 kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
 kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
 __call_rcu kernel/rcu/tree.c:3011 [inline]
 call_rcu+0x189/0x950 kernel/rcu/tree.c:3091
 gfs2_quota_cleanup+0x43c/0x6a0 fs/gfs2/quota.c:1490
 gfs2_make_fs_ro+0x440/0x620 fs/gfs2/super.c:561
 signal_our_withdraw fs/gfs2/util.c:166 [inline]
 gfs2_withdraw+0x610/0x1490 fs/gfs2/util.c:343
 gfs2_dinode_in fs/gfs2/glops.c:465 [inline]
 gfs2_inode_refresh+0xb64/0xff0 fs/gfs2/glops.c:485
 inode_go_lock+0x127/0x470 fs/gfs2/glops.c:510
 do_promote+0x741/0xab0 fs/gfs2/glock.c:507
 finish_xmote+0x4df/0xb00 fs/gfs2/glock.c:678
 do_xmote+0x7b6/0x1120 fs/gfs2/glock.c:824
 gfs2_glock_nq+0xc7a/0x1550 fs/gfs2/glock.c:1534
 gfs2_glock_nq_init fs/gfs2/glock.h:246 [inline]
 do_sync+0x4ab/0xc40 fs/gfs2/quota.c:927
 gfs2_quota_sync+0x32c/0x700 fs/gfs2/quota.c:1329
 gfs2_sync_fs+0x48/0xb0 fs/gfs2/super.c:651
 sync_filesystem+0xe6/0x220 fs/sync.c:56
 generic_shutdown_super+0x6b/0x300 fs/super.c:448
 kill_block_super+0x7c/0xe0 fs/super.c:1427
 deactivate_locked_super+0x93/0xf0 fs/super.c:335
 cleanup_mnt+0x42d/0x4e0 fs/namespace.c:1148
 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
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff8880550a2000
 which belongs to the cache gfs2_quotad of size 272
The buggy address is located 172 bytes inside of
 272-byte region [ffff8880550a2000, ffff8880550a2110)
The buggy address belongs to the page:
page:ffffea0001542880 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x550a2
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 dead000000000122 ffff8881468a5a00
raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Reclaimable, gfp_mask 0x112c50(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 6493, ts 171349373355, free_ts 163337682326
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1bbd/0x1ca0 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x80a/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x195/0x290 mm/slub.c:3238
 kmem_cache_zalloc include/linux/slab.h:728 [inline]
 qd_alloc+0x50/0x260 fs/gfs2/quota.c:216
 gfs2_quota_init+0x74e/0xea0 fs/gfs2/quota.c:1426
 gfs2_make_fs_rw+0x414/0x580 fs/gfs2/super.c:159
 gfs2_fill_super+0x1837/0x1f00 fs/gfs2/ops_fstype.c:1276
 get_tree_bdev+0x3f1/0x610 fs/super.c:1325
 gfs2_get_tree+0x4d/0x1e0 fs/gfs2/ops_fstype.c:1332
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x24a/0xa40 fs/namespace.c:3034
 do_mount fs/namespace.c:3377 [inline]
 __do_sys_mount fs/namespace.c:3585 [inline]
 __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3562
 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+0x8f/0x2a0 mm/page_alloc.c:3396
 free_slab mm/slub.c:2020 [inline]
 discard_slab mm/slub.c:2026 [inline]
 __unfreeze_partials+0x1a5/0x200 mm/slub.c:2512
 put_cpu_partial+0x12d/0x190 mm/slub.c:2592
 qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xd0 mm/kasan/common.c:444
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x100/0x290 mm/slub.c:3238
 __d_alloc+0x2a/0x6f0 fs/dcache.c:1749
 d_alloc fs/dcache.c:1828 [inline]
 d_alloc_parallel+0x7b/0x1330 fs/dcache.c:2584
 __lookup_slow+0x134/0x410 fs/namei.c:1656
 lookup_one_len+0x19d/0x2d0 fs/namei.c:2726
 start_creating+0x184/0x310 fs/debugfs/inode.c:354
 __debugfs_create_file+0x6f/0x510 fs/debugfs/inode.c:399
 kvm_create_vm_debugfs virt/kvm/kvm_main.c:1044 [inline]
 kvm_dev_ioctl_create_vm virt/kvm/kvm_main.c:4782 [inline]
 kvm_dev_ioctl+0x1d42/0x2070 virt/kvm/kvm_main.c:4809

Memory state around the buggy address:
 ffff8880550a1f80: fb fb fc fc fb fb fb fc fc fb fb fb fc fc fc fc
 ffff8880550a2000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880550a2080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8880550a2100: fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880550a2180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/23 06:36 linux-5.15.y b9d57c40a767 b10da5ec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in slot_put
2026/01/30 01:27 linux-5.15.y 9eec9a14ee10 bfa73b7b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in slot_put
* Struck through repros no longer work on HEAD.