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

Status: moderation: reported on 2025/10/07 11:49
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+3366add91c4b8d9822cf@syzkaller.appspotmail.com
First crash: 6d03h, last: 6d03h
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Read in seq_printf fs 19 5 150d 256d 0/29 auto-obsoleted due to no activity on 2025/08/09 17:54
upstream KMSAN: uninit-value in seq_printf (2) fs 7 C 99 1212d 1478d 0/29 auto-closed as invalid on 2022/09/30 02:43
android-5-10 KASAN: use-after-free Read in seq_printf 19 15 15d 122d 0/2 premoderation: reported on 2025/06/08 22:35
upstream KMSAN: kernel-infoleak in __skb_datagram_iter net 9 68 744d 849d 23/29 fixed on 2023/09/28 17:51
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf 19 2 19d 24d 0/2 premoderation: reported on 2025/09/15 09:58
android-5-15 KASAN: use-after-free Read in seq_printf 19 1 20d 20d 0/2 premoderation: reported on 2025/09/18 23:28

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in string_nocheck lib/vsprintf.c:653 [inline]
BUG: KASAN: slab-use-after-free in string+0x231/0x2b0 lib/vsprintf.c:735
Read of size 1 at addr ffff88807c8d4a20 by task syz.5.3726/20243

CPU: 0 UID: 0 PID: 20243 Comm: syz.5.3726 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 string_nocheck lib/vsprintf.c:653 [inline]
 string+0x231/0x2b0 lib/vsprintf.c:735
 vsnprintf+0x739/0xf00 lib/vsprintf.c:2926
 seq_vprintf fs/seq_file.c:391 [inline]
 seq_printf+0x178/0x270 fs/seq_file.c:406
 input_devices_seq_show+0x145/0x640 drivers/input/input.c:1133
 seq_read_iter+0x9b8/0xe20 fs/seq_file.c:272
 seq_read+0x369/0x480 fs/seq_file.c:162
 pde_read fs/proc/inode.c:308 [inline]
 proc_reg_read+0x1e9/0x2e0 fs/proc/inode.c:320
 vfs_read+0x200/0xa30 fs/read_write.c:570
 ksys_read+0x145/0x250 fs/read_write.c:715
 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: 0033:0x7f7d6bd8eec9
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:00007f7d69fd5038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f7d6bfe6180 RCX: 00007f7d6bd8eec9
RDX: 0000000000001906 RSI: 00002000000001c0 RDI: 0000000000000005
RBP: 00007f7d6be11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7d6bfe6218 R14: 00007f7d6bfe6180 R15: 00007f7d6c10fa28
 </TASK>

Allocated by task 1207:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:417
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __kmalloc_cache_noprof+0x3d5/0x6f0 mm/slub.c:5724
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 xpad_probe+0x428/0x1fc0 drivers/input/joystick/xpad.c:2075
 usb_probe_interface+0x665/0xc30 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x26d/0x9e0 drivers/base/dd.c:659
 __driver_probe_device+0x18c/0x2f0 drivers/base/dd.c:801
 driver_probe_device+0x4f/0x430 drivers/base/dd.c:831
 __device_attach_driver+0x2ce/0x530 drivers/base/dd.c:959
 bus_for_each_drv+0x24e/0x2e0 drivers/base/bus.c:462
 __device_attach+0x2b8/0x400 drivers/base/dd.c:1031
 bus_probe_device+0x185/0x260 drivers/base/bus.c:537
 device_add+0x7b6/0xb50 drivers/base/core.c:3689
 usb_set_configuration+0x1a87/0x20e0 drivers/usb/core/message.c:2210
 usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
 usb_probe_device+0x1c4/0x390 drivers/usb/core/driver.c:291
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x26d/0x9e0 drivers/base/dd.c:659
 __driver_probe_device+0x18c/0x2f0 drivers/base/dd.c:801
 driver_probe_device+0x4f/0x430 drivers/base/dd.c:831
 __device_attach_driver+0x2ce/0x530 drivers/base/dd.c:959
 bus_for_each_drv+0x24e/0x2e0 drivers/base/bus.c:462
 __device_attach+0x2b8/0x400 drivers/base/dd.c:1031
 bus_probe_device+0x185/0x260 drivers/base/bus.c:537
 device_add+0x7b6/0xb50 drivers/base/core.c:3689
 usb_new_device+0xa39/0x16f0 drivers/usb/core/hub.c:2694
 hub_port_connect drivers/usb/core/hub.c:5566 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x2958/0x4a20 drivers/usb/core/hub.c:5952
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 5908:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 __kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:587
 kasan_save_free_info mm/kasan/kasan.h:406 [inline]
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2514 [inline]
 slab_free mm/slub.c:6566 [inline]
 kfree+0x19a/0x6d0 mm/slub.c:6773
 xpad_disconnect+0x350/0x480 drivers/input/joystick/xpad.c:2259
 usb_unbind_interface+0x26e/0x910 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:571 [inline]
 __device_release_driver drivers/base/dd.c:1274 [inline]
 device_release_driver_internal+0x4d9/0x800 drivers/base/dd.c:1297
 bus_remove_device+0x34d/0x410 drivers/base/bus.c:579
 device_del+0x511/0x8e0 drivers/base/core.c:3878
 usb_disable_device+0x3e9/0x8a0 drivers/usb/core/message.c:1418
 usb_disconnect+0x330/0x950 drivers/usb/core/hub.c:2344
 hub_port_connect drivers/usb/core/hub.c:5406 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x1cf5/0x4a20 drivers/usb/core/hub.c:5952
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
 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:56
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:559
 insert_work+0x3d/0x330 kernel/workqueue.c:2186
 __queue_work+0xcd2/0xfb0 kernel/workqueue.c:2341
 queue_work_on+0x181/0x270 kernel/workqueue.c:2392
 queue_work include/linux/workqueue.h:669 [inline]
 schedule_work include/linux/workqueue.h:730 [inline]
 xpad360w_process_packet drivers/input/joystick/xpad.c:1026 [inline]
 xpad_irq_in+0xb57/0x2590 drivers/input/joystick/xpad.c:1252
 __usb_hcd_giveback_urb+0x376/0x540 drivers/usb/core/hcd.c:1661
 dummy_timer+0x862/0x4550 drivers/usb/gadget/udc/dummy_hcd.c:1995
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x529/0xc60 kernel/time/hrtimer.c:1841
 hrtimer_run_softirq+0x187/0x2b0 kernel/time/hrtimer.c:1858
 handle_softirqs+0x283/0x870 kernel/softirq.c:622
 do_softirq+0xec/0x180 kernel/softirq.c:523
 __local_bh_enable_ip+0x17d/0x1c0 kernel/softirq.c:450
 wg_socket_send_skb_to_peer+0x16b/0x1d0 drivers/net/wireguard/socket.c:184
 wg_packet_create_data_done drivers/net/wireguard/send.c:251 [inline]
 wg_packet_tx_worker+0x1c8/0x7c0 drivers/net/wireguard/send.c:276
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:56
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:559
 insert_work+0x3d/0x330 kernel/workqueue.c:2186
 __queue_work+0xcd2/0xfb0 kernel/workqueue.c:2341
 queue_work_on+0x181/0x270 kernel/workqueue.c:2392
 queue_work include/linux/workqueue.h:669 [inline]
 schedule_work include/linux/workqueue.h:730 [inline]
 xpad360w_process_packet drivers/input/joystick/xpad.c:1026 [inline]
 xpad_irq_in+0xb57/0x2590 drivers/input/joystick/xpad.c:1252
 __usb_hcd_giveback_urb+0x376/0x540 drivers/usb/core/hcd.c:1661
 dummy_timer+0x862/0x4550 drivers/usb/gadget/udc/dummy_hcd.c:1995
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x529/0xc60 kernel/time/hrtimer.c:1841
 hrtimer_run_softirq+0x187/0x2b0 kernel/time/hrtimer.c:1858
 handle_softirqs+0x283/0x870 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:723
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1052
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

The buggy address belongs to the object at ffff88807c8d4800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 544 bytes inside of
 freed 1024-byte region [ffff88807c8d4800, ffff88807c8d4c00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88807c8d4800 pfn:0x7c8d0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff88813fe26dc0 ffffea0001625410 ffffea0001bf4c10
raw: ffff88807c8d4800 000000000010000c 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fe26dc0 ffffea0001625410 ffffea0001bf4c10
head: ffff88807c8d4800 000000000010000c 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001f23401 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5857, tgid 5857 (syz-executor), ts 82559481002, free_ts 49293548386
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1850
 prep_new_page mm/page_alloc.c:1858 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3884
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:3030 [inline]
 allocate_slab+0x96/0x3a0 mm/slub.c:3203
 new_slab mm/slub.c:3257 [inline]
 ___slab_alloc+0xe94/0x1920 mm/slub.c:4627
 __slab_alloc+0x65/0x100 mm/slub.c:4746
 __slab_alloc_node mm/slub.c:4822 [inline]
 slab_alloc_node mm/slub.c:5233 [inline]
 __do_kmalloc_node mm/slub.c:5602 [inline]
 __kvmalloc_node_noprof+0x6ba/0x910 mm/slub.c:7036
 bucket_table_alloc lib/rhashtable.c:186 [inline]
 rhashtable_init_noprof+0x4f3/0xbc0 lib/rhashtable.c:1075
 nsim_fib_create+0x316/0x9d0 drivers/net/netdevsim/fib.c:1570
 nsim_drv_probe+0x778/0xba0 drivers/net/netdevsim/dev.c:1631
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x26d/0x9e0 drivers/base/dd.c:659
 __driver_probe_device+0x18c/0x2f0 drivers/base/dd.c:801
 driver_probe_device+0x4f/0x430 drivers/base/dd.c:831
 __device_attach_driver+0x2ce/0x530 drivers/base/dd.c:959
 bus_for_each_drv+0x24e/0x2e0 drivers/base/bus.c:462
page last free pid 5582 tgid 5582 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2906
 discard_slab mm/slub.c:3301 [inline]
 __put_partials+0x146/0x170 mm/slub.c:3848
 put_cpu_partial+0x1f2/0x2e0 mm/slub.c:3923
 __slab_free+0x2b9/0x390 mm/slub.c:5882
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:352
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4946 [inline]
 slab_alloc_node mm/slub.c:5245 [inline]
 __kmalloc_cache_noprof+0x36f/0x6f0 mm/slub.c:5719
 kmalloc_noprof include/linux/slab.h:957 [inline]
 tomoyo_print_header security/tomoyo/audit.c:156 [inline]
 tomoyo_init_log+0x183/0x1f70 security/tomoyo/audit.c:255
 tomoyo_supervisor+0x340/0x1480 security/tomoyo/common.c:2198
 tomoyo_audit_path_log security/tomoyo/file.c:168 [inline]
 tomoyo_path_permission+0x25a/0x380 security/tomoyo/file.c:587
 tomoyo_check_open_permission+0x24d/0x3b0 security/tomoyo/file.c:777
 security_file_open+0xb1/0x270 security/security.c:3183
 do_dentry_open+0x384/0x13f0 fs/open.c:942
 vfs_open+0x3b/0x340 fs/open.c:1095
 do_open fs/namei.c:3975 [inline]
 path_openat+0x2ee5/0x3830 fs/namei.c:4134

Memory state around the buggy address:
 ffff88807c8d4900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807c8d4980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807c8d4a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff88807c8d4a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807c8d4b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/03 11:42 upstream e406d57be7bd 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: slab-use-after-free Read in seq_printf
* Struck through repros no longer work on HEAD.