KASAN: slab-use-after-free Write in release_tty

Status: upstream: reported C repro on 2026/08/11 02:03
Subsystems: serial
Labels: prio:normal actionable
[Documentation on labels]
Reported-by: syzbot+bca09f5d8b843bbf7571@syzkaller.appspotmail.com
First crash: 8d09h, last: 9h30m
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
5d035092 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Write in release_tty 2026/08/11 01:49 2026/08/11 01:49 2026/08/11 02:02 039457bd
934519cc assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Write in release_tty 2026/08/09 06:08 2026/08/09 06:08 2026/08/09 06:17 5d63f80b
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [serial?] KASAN: slab-use-after-free Write in release_tty 0 (2) 2026/08/14 03:07
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Write in release_tty 22 1 4d02h 4d02h 0/2 premoderation: reported on 2026/08/10 10:24

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in release_tty+0x36b/0x560 drivers/tty/tty_io.c:1584
Write of size 8 at addr ffff888027479120 by task syz-executor331/5612

CPU: 1 UID: 0 PID: 5612 Comm: syz-executor331 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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
 release_tty+0x36b/0x560 drivers/tty/tty_io.c:1584
 tty_release_struct+0xb8/0xd0 drivers/tty/tty_io.c:1692
 tty_release+0xc6b/0x1680 drivers/tty/tty_io.c:1852
 __fput+0x42a/0xa80 fs/file_table.c:512
 fput_close_sync+0x11f/0x240 fs/file_table.c:617
 __do_sys_close fs/open.c:1511 [inline]
 __se_sys_close fs/open.c:1496 [inline]
 __x64_sys_close+0x7e/0x110 fs/open.c:1496
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5468aadc0e
Code: 08 0f 85 65 e1 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08
RSP: 002b:00007ffe95c075a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 000055558acba400 RCX: 00007f5468aadc0e
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000182c2
R13: 00000000000182f4 R14: 00007f5468b4ab2c R15: 00007f5468b4ab20
 </TASK>

Allocated by task 5613:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x3d2/0x6b0 mm/slub.c:5489
 _kmalloc_noprof include/linux/slab.h:988 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 gs_port_alloc drivers/usb/gadget/function/u_serial.c:1218 [inline]
 gserial_alloc_line_no_console+0x23a/0x6e0 drivers/usb/gadget/function/u_serial.c:1298
 gserial_alloc_line+0x18/0x90 drivers/usb/gadget/function/u_serial.c:1332
 acm_alloc_instance+0xc7/0x140 drivers/usb/gadget/function/f_acm.c:891
 try_get_usb_function_instance drivers/usb/gadget/functions.c:28 [inline]
 usb_get_function_instance+0xe3/0x2f0 drivers/usb/gadget/functions.c:44
 function_make+0x127/0x360 drivers/usb/gadget/configfs.c:626
 configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1360
 vfs_mkdir+0x402/0x620 fs/namei.c:5276
 filename_mkdirat+0x289/0x520 fs/namei.c:5309
 __do_sys_mkdirat fs/namei.c:5330 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5327
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5613:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 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:2677 [inline]
 slab_free mm/slub.c:6377 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6692
 gserial_free_port+0x248/0x2c0 drivers/usb/gadget/function/u_serial.c:1262
 gserial_free_line+0xc3/0x1f0 drivers/usb/gadget/function/u_serial.c:1279
 acm_free_instance+0x39/0x60 drivers/usb/gadget/function/f_acm.c:875
 usb_put_function_instance+0x90/0xb0 drivers/usb/gadget/functions.c:77
 config_item_cleanup fs/configfs/item.c:128 [inline]
 config_item_release+0x13a/0x2d0 fs/configfs/item.c:137
 configfs_rmdir+0x885/0x950 fs/configfs/dir.c:1571
 vfs_rmdir+0x3e9/0x6b0 fs/namei.c:5381
 filename_rmdir+0x292/0x520 fs/namei.c:5438
 __do_sys_rmdir fs/namei.c:5461 [inline]
 __se_sys_rmdir+0x2e/0x140 fs/namei.c:5458
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888027479000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 288 bytes inside of
 freed 2048-byte region [ffff888027479000, ffff888027479800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27478
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813ffb2000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813ffb2000 dead000000000100 dead000000000122
head: 0000000000000000 0000000800080008 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 765, tgid 765 (kworker/u8:6), ts 8666777166, free_ts 8122171962
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x262a/0x26a0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3266 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3380
 new_slab mm/slub.c:3426 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7310
 refill_sheaf mm/slub.c:2804 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4675
 alloc_from_pcs mm/slub.c:4773 [inline]
 slab_alloc_node mm/slub.c:4905 [inline]
 __do_kmalloc_node mm/slub.c:5333 [inline]
 __kmalloc_noprof+0x544/0x780 mm/slub.c:5359
 _kmalloc_noprof include/linux/slab.h:992 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 scsi_alloc_target+0x138/0xbc0 drivers/scsi/scsi_scan.c:505
 __scsi_scan_target+0x164/0xe10 drivers/scsi/scsi_scan.c:1780
 scsi_scan_channel drivers/scsi/scsi_scan.c:1885 [inline]
 scsi_scan_host_selected+0x36e/0x680 drivers/scsi/scsi_scan.c:1914
 do_scsi_scan_host drivers/scsi/scsi_scan.c:2047 [inline]
 do_scan_async+0x10e/0x660 drivers/scsi/scsi_scan.c:2057
 async_run_entry_fn+0x9d/0x430 kernel/async.c:129
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
page last free pid 10 tgid 10 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 free_pages_prepare+0x946/0xa40 mm/page_alloc.c:1451
 __free_contig_range_common+0x174/0x340 mm/page_alloc.c:6897
 __free_contig_range mm/page_alloc.c:6942 [inline]
 free_pages_bulk+0x48/0x120 mm/page_alloc.c:5257
 vm_area_free_pages mm/vmalloc.c:3461 [inline]
 vfree+0x26f/0x510 mm/vmalloc.c:3510
 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3414
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 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

Memory state around the buggy address:
 ffff888027479000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888027479080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888027479100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888027479180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888027479200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/14 03:07 upstream 3aa1dcaa4f6f b13552fe .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Write in release_tty
2026/08/06 03:02 upstream 0d8395707651 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Write in release_tty
* Struck through repros no longer work on HEAD.