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

Status: premoderation: reported on 2026/09/23 06:02
Reported-by: syzbot+2639b0a8b6a0d6cf6d3e@syzkaller.appspotmail.com
First crash: 4d09h, last: 2d08h
▶ ▼ Similar bugs (14)
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 503d 609d 0/29 auto-obsoleted due to no activity on 2025/08/09 17:54
upstream KASAN: slab-use-after-free Read in seq_printf prio:high fs 19 70 1d18h 8d12h 0/29 upstream: reported on 2026/09/19 02:15
linux-6.6 KASAN: slab-use-after-free Read in seq_printf 19 1 33d 33d 0/2 upstream: reported on 2026/08/25 13:48
android-5-15 KASAN: use-after-free Read in seq_printf (2) 19 10 5h10m 32d 0/2 premoderation: reported on 2026/08/26 02:30
upstream KMSAN: uninit-value in seq_printf (2) fs 7 syz, C 99 1565d 1831d 0/29 auto-closed as invalid on 2022/09/30 02:43
linux-5.15 KASAN: use-after-free Read in seq_printf 19 1 4d00h 4d00h 0/3 upstream: reported on 2026/09/23 14:29
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf (2) 17 1 175d 175d 0/2 auto-obsoleted due to no activity on 2026/07/03 17:29
android-5-10 KASAN: use-after-free Read in seq_printf (3) 19 8 12h11m 28d 0/2 premoderation: reported on 2026/08/30 00:45
android-5-10 KASAN: use-after-free Read in seq_printf 19 15 368d 475d 0/2 auto-obsoleted due to no activity on 2025/12/23 06:43
upstream KMSAN: kernel-infoleak in __skb_datagram_iter net 9 68 1097d 1202d 23/29 fixed on 2023/09/28 17:51
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf 19 2 372d 377d 0/2 auto-obsoleted due to no activity on 2025/12/19 00:57
android-5-10 KASAN: use-after-free Read in seq_printf (2) 19 1 255d 255d 0/2 auto-obsoleted due to no activity on 2026/04/14 16:00
android-6-1 KASAN: use-after-free Read in seq_printf 19 syz, C 6 5h40m 2d17h 0/2 upstream: reported C repro on 2026/09/24 21:21
android-5-15 KASAN: use-after-free Read in seq_printf 19 1 373d 373d 0/2 auto-obsoleted due to no activity on 2025/12/17 23:30

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in string_nocheck lib/vsprintf.c:646 [inline]
BUG: KASAN: slab-use-after-free in string+0x20f/0x2b0 lib/vsprintf.c:728
Read of size 1 at addr ffff888104ea21c0 by task syz.2.283/1312

CPU: 1 UID: 0 PID: 1312 Comm: syz.2.283 Not tainted syzkaller #0 ffcc03b7087851531ca4478bc989862769751c2e
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 print_address_description+0x71/0x210 mm/kasan/report.c:377
 print_report+0x4a/0x70 mm/kasan/report.c:481
 kasan_report+0x162/0x1a0 mm/kasan/report.c:594
 __asan_report_load1_noabort+0x18/0x20 mm/kasan/report_generic.c:378
 string_nocheck lib/vsprintf.c:646 [inline]
 string+0x20f/0x2b0 lib/vsprintf.c:728
 vsnprintf+0xe65/0x1ad0 lib/vsprintf.c:2803
 seq_vprintf fs/seq_file.c:391 [inline]
 seq_printf+0x189/0x290 fs/seq_file.c:406
 show_interrupts+0x6d2/0x7f0 kernel/irq/proc.c:524
 seq_read_iter+0xa80/0xf30 fs/seq_file.c:272
 proc_reg_read_iter+0x1e7/0x2c0 fs/proc/inode.c:299
 new_sync_read fs/read_write.c:489 [inline]
 vfs_read+0x60e/0xc70 fs/read_write.c:570
 ksys_read+0x145/0x260 fs/read_write.c:713
 __do_sys_read fs/read_write.c:723 [inline]
 __se_sys_read fs/read_write.c:721 [inline]
 __x64_sys_read+0x7f/0x90 fs/read_write.c:721
 x64_sys_call+0x2638/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fa4d159e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa4d23dd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fa4d1826090 RCX: 00007fa4d159e159
RDX: 00000000000000bd RSI: 0000200000006a00 RDI: 0000000000000005
RBP: 00007fa4d163506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa4d1826128 R14: 00007fa4d1826090 R15: 00007ffc9ca1d138
 </TASK>

Allocated by task 855:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_alloc_info+0x3a/0x50 mm/kasan/generic.c:565
 poison_kmalloc_redzone mm/kasan/common.c:379 [inline]
 __kasan_kmalloc+0x96/0xb0 mm/kasan/common.c:396
 kasan_kmalloc include/linux/kasan.h:261 [inline]
 __do_kmalloc_node mm/slub.c:4395 [inline]
 __kmalloc_node_track_caller_noprof+0x24e/0x4f0 mm/slub.c:4414
 kvasprintf+0xf1/0x260 lib/kasprintf.c:25
 kvasprintf_const+0xf6/0x250 lib/kasprintf.c:49
 kobject_set_name_vargs+0x65/0x120 lib/kobject.c:274
 kobject_add_varg lib/kobject.c:368 [inline]
 kobject_init_and_add+0xef/0x1a0 lib/kobject.c:457
 netdev_queue_add_kobject net/core/net-sysfs.c:1785 [inline]
 netdev_queue_update_kobjects+0x209/0x550 net/core/net-sysfs.c:1837
 register_queue_kobjects net/core/net-sysfs.c:1899 [inline]
 netdev_register_kobject+0x283/0x330 net/core/net-sysfs.c:2139
 register_netdevice+0x1042/0x1a80 net/core/dev.c:10621
 register_netdev+0x42/0x60 net/core/dev.c:10758
 loopback_net_init+0x78/0x160 drivers/net/loopback.c:217
 ops_init+0x2ff/0x5d0 net/core/net_namespace.c:139
 setup_net+0x227/0x9b0 net/core/net_namespace.c:356
 copy_net_ns+0x4fc/0xa20 net/core/net_namespace.c:510
 create_new_namespaces+0x390/0x6f0 kernel/nsproxy.c:110
 copy_namespaces+0x257/0x2b0 kernel/nsproxy.c:179
 copy_process+0x12d5/0x3350 kernel/fork.c:2432
 kernel_clone+0x233/0x810 kernel/fork.c:2851
 __do_sys_clone kernel/fork.c:2996 [inline]
 __se_sys_clone kernel/fork.c:2980 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:2980
 x64_sys_call+0x2b3c/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 596:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_free_info+0x44/0x50 mm/kasan/generic.c:579
 poison_slab_object mm/kasan/common.c:249 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:266
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2445 [inline]
 slab_free mm/slub.c:4714 [inline]
 kfree+0x158/0x440 mm/slub.c:4875
 kfree_const+0x3d/0x50 mm/util.c:49
 kobject_cleanup lib/kobject.c:695 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x21f/0x2a0 lib/kobject.c:737
 netdev_queue_update_kobjects+0x4b0/0x550 net/core/net-sysfs.c:1853
 remove_queue_kobjects net/core/net-sysfs.c:1950 [inline]
 netdev_unregister_kobject+0x104/0x260 net/core/net-sysfs.c:2103
 unregister_netdevice_many_notify+0x1678/0x1be0 net/core/dev.c:11567
 unregister_netdevice_many net/core/dev.c:11595 [inline]
 default_device_exit_batch+0x845/0x8d0 net/core/dev.c:12166
 ops_exit_list net/core/net_namespace.c:178 [inline]
 cleanup_net+0x744/0xc90 net/core/net_namespace.c:642
 process_one_work kernel/workqueue.c:3273 [inline]
 process_scheduled_works+0x7f7/0x1060 kernel/workqueue.c:3354
 worker_thread+0xc99/0x13f0 kernel/workqueue.c:3435
 kthread+0x2c7/0x360 kernel/kthread.c:389
 ret_from_fork+0x64/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

The buggy address belongs to the object at ffff888104ea21c0
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 freed 8-byte region [ffff888104ea21c0, ffff888104ea21c8)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888104ea2720 pfn:0x104ea2
flags: 0x4000000000000200(workingset|zone=1)
page_type: f5(slab)
raw: 4000000000000200 ffff888100041500 ffffea00045c6750 ffffea00042daa90
raw: ffff888104ea2720 000000000080007e 00000001f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 2749443219, free_ts 0
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook+0x37d/0x3b0 mm/page_alloc.c:1863
 prep_new_page+0x2d/0x180 mm/page_alloc.c:1871
 get_page_from_freelist+0x4aea/0x4ba0 mm/page_alloc.c:3948
 __alloc_pages_noprof+0x35a/0x7e0 mm/page_alloc.c:5315
 alloc_slab_page+0x6b/0x1e0 mm/slub.c:-1
 allocate_slab+0x69/0x430 mm/slub.c:2687
 new_slab mm/slub.c:2741 [inline]
 ___slab_alloc+0x591/0x8c0 mm/slub.c:3934
 __slab_alloc mm/slub.c:4025 [inline]
 __slab_alloc_node mm/slub.c:4078 [inline]
 slab_alloc_node mm/slub.c:4239 [inline]
 __do_kmalloc_node mm/slub.c:4394 [inline]
 __kmalloc_noprof+0x2fc/0x510 mm/slub.c:4407
 kmalloc_noprof include/linux/slab.h:886 [inline]
 acpi_ex_allocate_name_string+0xed/0x420 drivers/acpi/acpica/exnames.c:66
 acpi_ex_get_name_string+0x2a7/0x490 drivers/acpi/acpica/exnames.c:367
 acpi_ds_create_operand+0x16c/0x8c0 drivers/acpi/acpica/dsutils.c:446
 acpi_ds_create_operands+0x275/0x420 drivers/acpi/acpica/dsutils.c:707
 acpi_ds_exec_end_op+0x28e/0x1210 drivers/acpi/acpica/dswexec.c:385
 acpi_ps_parse_loop+0xc80/0x1ac0 drivers/acpi/acpica/psloop.c:525
 acpi_ps_parse_aml+0x218/0x9b0 drivers/acpi/acpica/psparse.c:475
 acpi_ps_execute_method+0x69e/0x7d0 drivers/acpi/acpica/psxface.c:190
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888104ea2080: fa fc fc fc fa fc fc fc 00 fc fc fc 00 fc fc fc
 ffff888104ea2100: 00 fc fc fc 00 fc fc fc fa fc fc fc fa fc fc fc
>ffff888104ea2180: fa fc fc fc fa fc fc fc fa fc fc fc 00 fc fc fc
                                           ^
 ffff888104ea2200: 06 fc fc fc fa fc fc fc 00 fc fc fc fa fc fc fc
 ffff888104ea2280: 00 fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/25 07:02 android16-6.12 558b94a8d268 f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/09/25 01:53 android16-6.12 558b94a8d268 3c3cdf19 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/09/23 06:01 android16-6.12 c8909f7cf138 5207b90e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
* Struck through repros no longer work on HEAD.