syzbot


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

Status: moderation: reported on 2025/06/29 21:30
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+aebdfea6c19921287ac3@syzkaller.appspotmail.com
First crash: 10d, last: 10d

Sample crash report:
ntfs3(loop0): ino=5, mi_enum_attr
ntfs3(loop0): ino=21, "bus" failed to open parent directory r=5 to update
==================================================================
BUG: KASAN: slab-use-after-free in file_f_owner include/linux/fs.h:1181 [inline]
BUG: KASAN: slab-use-after-free in dnotify_handle_event+0x13f/0x440 fs/notify/dnotify/dnotify.c:112
Read of size 8 at addr ffff88803012a938 by task syz.0.615/8490

CPU: 0 UID: 0 PID: 8490 Comm: syz.0.615 Not tainted 6.16.0-rc3-next-20250625-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xd2/0x2b0 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 file_f_owner include/linux/fs.h:1181 [inline]
 dnotify_handle_event+0x13f/0x440 fs/notify/dnotify/dnotify.c:112
 fsnotify_handle_event fs/notify/fsnotify.c:350 [inline]
 send_to_group fs/notify/fsnotify.c:424 [inline]
 fsnotify+0x1671/0x1a80 fs/notify/fsnotify.c:641
 __fsnotify_parent+0x3fe/0x540 fs/notify/fsnotify.c:287
 fsnotify_parent include/linux/fsnotify.h:96 [inline]
 fsnotify_path include/linux/fsnotify.h:113 [inline]
 fsnotify_file include/linux/fsnotify.h:127 [inline]
 fsnotify_modify include/linux/fsnotify.h:458 [inline]
 vfs_write+0x7d6/0xa90 fs/read_write.c:690
 ksys_pwrite64 fs/read_write.c:793 [inline]
 __do_sys_pwrite64 fs/read_write.c:801 [inline]
 __se_sys_pwrite64 fs/read_write.c:798 [inline]
 __x64_sys_pwrite64+0x193/0x220 fs/read_write.c:798
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f22e098e929
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:00007f22e17b7038 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007f22e0bb6080 RCX: 00007f22e098e929
RDX: 0000000000000001 RSI: 0000200000000100 RDI: 0000000000000004
RBP: 00007f22e0a10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000511 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f22e0bb6080 R15: 00007ffe8d654338
 </TASK>

Allocated by task 8490:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:319 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:345
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4180 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4236
 alloc_empty_file+0x55/0x1d0 fs/file_table.c:237
 path_openat+0x107/0x3830 fs/namei.c:4032
 do_filp_open+0x1fa/0x410 fs/namei.c:4073
 do_sys_openat2+0x121/0x1c0 fs/open.c:1434
 do_sys_open fs/open.c:1449 [inline]
 __do_sys_open fs/open.c:1457 [inline]
 __se_sys_open fs/open.c:1453 [inline]
 __x64_sys_open+0x11e/0x150 fs/open.c:1453
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 8483:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x62/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2417 [inline]
 slab_free_after_rcu_debug+0x129/0x2a0 mm/slub.c:4730
 rcu_do_batch kernel/rcu/tree.c:2582 [inline]
 rcu_core+0xca8/0x1710 kernel/rcu/tree.c:2838
 handle_softirqs+0x286/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:47
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:548
 slab_free_hook mm/slub.c:2378 [inline]
 slab_free mm/slub.c:4680 [inline]
 kmem_cache_free+0x2f6/0x400 mm/slub.c:4782
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:114
 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:47
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:548
 task_work_add+0xb1/0x420 kernel/task_work.c:65
 __fput_deferred+0x154/0x390 fs/file_table.c:529
 fput_close+0x119/0x200 fs/file_table.c:585
 filp_close+0x27/0x40 fs/open.c:1560
 __range_close fs/file.c:752 [inline]
 __do_sys_close_range fs/file.c:811 [inline]
 __se_sys_close_range+0x359/0x650 fs/file.c:775
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88803012a8c0
 which belongs to the cache filp of size 360
The buggy address is located 120 bytes inside of
 freed 360-byte region [ffff88803012a8c0, ffff88803012aa28)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3012a
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88805d54db01
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801bad6a00 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000120012 00000000f5000000 ffff88805d54db01
head: 00fff00000000040 ffff88801bad6a00 dead000000000122 0000000000000000
head: 0000000000000000 0000000000120012 00000000f5000000 ffff88805d54db01
head: 00fff00000000001 ffffea0000c04a81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 8494, tgid 8493 (syz.8.619), ts 335345757165, free_ts 312445557128
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1848
 prep_new_page mm/page_alloc.c:1856 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3855
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5145
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2487 [inline]
 allocate_slab+0x8a/0x370 mm/slub.c:2655
 new_slab mm/slub.c:2709 [inline]
 ___slab_alloc+0xbeb/0x1410 mm/slub.c:3891
 __slab_alloc mm/slub.c:3981 [inline]
 __slab_alloc_node mm/slub.c:4056 [inline]
 slab_alloc_node mm/slub.c:4217 [inline]
 kmem_cache_alloc_noprof+0x283/0x3c0 mm/slub.c:4236
 alloc_empty_file+0x55/0x1d0 fs/file_table.c:237
 alloc_file fs/file_table.c:354 [inline]
 alloc_file_pseudo+0x13d/0x210 fs/file_table.c:383
 sock_alloc_file+0xb8/0x2e0 net/socket.c:470
 sock_map_fd net/socket.c:500 [inline]
 __sys_socket+0x13d/0x1b0 net/socket.c:1740
 __do_sys_socket net/socket.c:1745 [inline]
 __se_sys_socket net/socket.c:1743 [inline]
 __x64_sys_socket+0x7a/0x90 net/socket.c:1743
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 15 tgid 15 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1392 [inline]
 __free_frozen_pages+0xb80/0xd80 mm/page_alloc.c:2892
 rcu_do_batch kernel/rcu/tree.c:2582 [inline]
 rcu_core+0xca8/0x1710 kernel/rcu/tree.c:2838
 handle_softirqs+0x286/0x870 kernel/softirq.c:579
 run_ksoftirqd+0x9b/0x100 kernel/softirq.c:968
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff88803012a800: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
 ffff88803012a880: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff88803012a900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff88803012a980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803012aa00: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/25 21:21 linux-next 1b152eeca84a 26d77996 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in dnotify_handle_event
* Struck through repros no longer work on HEAD.