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2002:a05:6820:2086:b0:6ac:a994:8794 with SMTP id 006d021491bc7-6b11dce8389mr129600eaf.7.1786971936247; Mon, 17 Aug 2026 06:05:36 -0700 (PDT) Date: Mon, 17 Aug 2026 06:05:36 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a830720.dbb3a75c.20434b.005b.GAE@google.com> Subject: [syzbot] [serial?] KASAN: slab-use-after-free Read in check_tty_count From: syzbot To: gregkh@linuxfoundation.org, jirislaby@kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 3d6d817622b0 Merge tag 'scsi-fixes' of git://git.kernel.or.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=12961c79580000 kernel config: https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307 dashboard link: https://syzkaller.appspot.com/bug?extid=39a2135de1558208d3b3 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=171ff479580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15f92c79580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-3d6d8176.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/f486efba4dfc/vmlinux-3d6d8176.xz kernel image: https://storage.googleapis.com/syzbot-assets/9b9dcf9ee9f3/bzImage-3d6d8176.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+39a2135de1558208d3b3@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:82 [inline] BUG: KASAN: slab-use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] BUG: KASAN: slab-use-after-free in tty_port_kopened include/linux/tty_port.h:234 [inline] BUG: KASAN: slab-use-after-free in check_tty_count+0x134/0x2b0 drivers/tty/tty_io.c:287 Read of size 8 at addr ffff88802e4c4230 by task syz.2.21/6005 CPU: 0 UID: 0 PID: 6005 Comm: syz.2.21 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0x13d/0x4b0 mm/kasan/report.c:482 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:186 [inline] kasan_check_range+0x10f/0x1e0 mm/kasan/generic.c:200 instrument_atomic_read include/linux/instrumented.h:82 [inline] _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] tty_port_kopened include/linux/tty_port.h:234 [inline] check_tty_count+0x134/0x2b0 drivers/tty/tty_io.c:287 tty_release+0x95/0x1300 drivers/tty/tty_io.c:1728 __fput+0x3ff/0xb50 fs/file_table.c:512 task_work_run+0x150/0x240 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:70 [inline] exit_to_user_mode_loop+0x1d8/0x6f0 kernel/entry/common.c:101 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline] do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fce91f9e0d9 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:00007ffc8e0021f8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007fce92227da0 RCX: 00007fce91f9e0d9 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007fce92227da0 R08: 00007fce92226038 R09: 0000000000000000 R10: 000000000003fd94 R11: 0000000000000246 R12: 000000000000e659 R13: 00007fce92225fac R14: 000000000000e352 R15: 00007ffc8e002300 Allocated by task 6007: kasan_save_stack+0x30/0x50 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x2e5/0x6c0 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+0xac/0x710 drivers/usb/gadget/function/u_serial.c:1298 gserial_alloc_line+0x16/0xa0 drivers/usb/gadget/function/u_serial.c:1332 acm_alloc_instance+0xd9/0x160 drivers/usb/gadget/function/f_acm.c:891 try_get_usb_function_instance+0x136/0x1f0 drivers/usb/gadget/functions.c:28 usb_get_function_instance+0x16/0x70 drivers/usb/gadget/functions.c:44 function_make+0x18c/0x3f0 drivers/usb/gadget/configfs.c:626 configfs_mkdir+0x51e/0xb70 fs/configfs/dir.c:1360 vfs_mkdir+0x361/0x850 fs/namei.c:5276 filename_mkdirat+0x48b/0x5e0 fs/namei.c:5309 __do_sys_mkdirat fs/namei.c:5330 [inline] __se_sys_mkdirat fs/namei.c:5327 [inline] __x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5327 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 6007: kasan_save_stack+0x30/0x50 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5f/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+0x22b/0x6c0 mm/slub.c:6692 gserial_free_port+0x146/0x2f0 drivers/usb/gadget/function/u_serial.c:1262 gserial_free_line+0xf8/0x1e0 drivers/usb/gadget/function/u_serial.c:1279 acm_free_instance+0x3b/0x60 drivers/usb/gadget/function/f_acm.c:875 usb_put_function_instance+0x89/0xc0 drivers/usb/gadget/functions.c:77 config_item_cleanup+0x146/0x240 fs/configfs/item.c:128 config_item_release fs/configfs/item.c:137 [inline] kref_put include/linux/kref.h:65 [inline] config_item_put fs/configfs/item.c:149 [inline] config_item_put+0x93/0xb0 fs/configfs/item.c:146 configfs_rmdir+0x5e3/0x950 fs/configfs/dir.c:1571 vfs_rmdir fs/namei.c:5381 [inline] vfs_rmdir+0x328/0x8a0 fs/namei.c:5354 filename_rmdir+0x31a/0x5c0 fs/namei.c:5438 __do_sys_rmdir fs/namei.c:5461 [inline] __se_sys_rmdir fs/namei.c:5458 [inline] __x64_sys_rmdir+0x46/0x70 fs/namei.c:5458 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88802e4c4000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 560 bytes inside of freed 2048-byte region [ffff88802e4c4000, ffff88802e4c4800) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2e4c0 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000040 ffff88801bc42f00 dead000000000100 dead000000000122 raw: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000 head: 00fff00000000040 ffff88801bc42f00 dead000000000100 dead000000000122 head: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000 head: 00fff00000000003 fffffffffffffe01 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 5827, tgid 5827 (kworker/2:4), ts 58184228669, free_ts 57556351194 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1859 prep_new_page mm/page_alloc.c:1867 [inline] get_page_from_freelist+0xf48/0x3530 mm/page_alloc.c:3946 __alloc_frozen_pages_noprof+0x299/0x2dc0 mm/page_alloc.c:5304 alloc_slab_page mm/slub.c:3266 [inline] allocate_slab mm/slub.c:3380 [inline] new_slab+0xa2/0x640 mm/slub.c:3426 refill_objects+0xe3/0x410 mm/slub.c:7310 refill_sheaf mm/slub.c:2804 [inline] __pcs_replace_empty_main+0x376/0x680 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_node_track_caller_noprof+0x679/0x830 mm/slub.c:5471 kmalloc_reserve+0xe8/0x350 net/core/skbuff.c:637 __alloc_skb+0x185/0x710 net/core/skbuff.c:715 alloc_skb include/linux/skbuff.h:1384 [inline] mld_newpack.isra.0+0x18e/0xa20 net/ipv6/mcast.c:1789 add_grhead+0x299/0x340 net/ipv6/mcast.c:1900 add_grec+0x1389/0x1930 net/ipv6/mcast.c:2039 mld_send_cr net/ipv6/mcast.c:2164 [inline] mld_ifc_work+0x3c5/0xc10 net/ipv6/mcast.c:2710 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322 process_scheduled_works kernel/workqueue.c:3405 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486 kthread+0x370/0x450 kernel/kthread.c:436 page last free pid 5850 tgid 5850 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1406 [inline] __free_frozen_pages+0x79f/0x1090 mm/page_alloc.c:2950 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4584 [inline] slab_alloc_node mm/slub.c:4917 [inline] kmem_cache_alloc_noprof+0x26b/0x6a0 mm/slub.c:4931 __kernfs_new_node+0xd2/0xa10 fs/kernfs/dir.c:665 kernfs_new_node+0x117/0x150 fs/kernfs/dir.c:751 __kernfs_create_file+0x53/0x350 fs/kernfs/file.c:1050 sysfs_add_file_mode_ns+0x207/0x3c0 fs/sysfs/file.c:316 create_files fs/sysfs/group.c:82 [inline] internal_create_group+0x593/0xfb0 fs/sysfs/group.c:189 internal_create_groups+0x9d/0x150 fs/sysfs/group.c:229 device_add_groups drivers/base/core.c:2907 [inline] device_add_attrs drivers/base/core.c:2971 [inline] device_add+0x71a/0x1970 drivers/base/core.c:3711 netdev_register_kobject+0x1df/0x410 net/core/net-sysfs.c:2340 register_netdevice+0x15b6/0x25a0 net/core/dev.c:11446 nsim_init_netdevsim drivers/net/netdevsim/netdev.c:1070 [inline] nsim_create+0xc93/0x1420 drivers/net/netdevsim/netdev.c:1152 __nsim_dev_port_add+0x3ba/0x8f0 drivers/net/netdevsim/dev.c:1509 Memory state around the buggy address: ffff88802e4c4100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88802e4c4180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88802e4c4200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88802e4c4280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88802e4c4300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup