From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f69.google.com (mail-oo1-f69.google.com [209.85.161.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C072E48EBEE for ; Fri, 4 Sep 2026 12:38:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.69 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788525513; cv=none; b=OB7G6coioRHWQimKOcTin/BMe8m0zcWwrQTUftCkfJ38ZrYSEMJ3CCZLzO6V1EOlwFRQBiuKg+Y6hHj12lvLBlxLPBMKsVP72viipSDHLPSNR9N0yp3h75ap/neyCnGXF+c/WB4XDQ9bxpwNRaKyOTWvv+D7o0HhLCJJlpKKkjM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788525513; c=relaxed/simple; bh=SpaLZ03RIJGou3TA4o2D1zJ3OfKRLfVn0OAPE7ms6Uw=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; 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2002:a05:6820:2912:b0:6b7:46fc:1cd with SMTP id 006d021491bc7-6b746fc03a5mr2488644eaf.44.1788525509283; Fri, 04 Sep 2026 05:38:29 -0700 (PDT) Date: Fri, 04 Sep 2026 05:38:29 -0700 In-Reply-To: <6a6c3d48.5cf34cee.28a846.0008.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a9abbc5.efa90033.8a9e.0005.GAE@google.com> Subject: Re: [syzbot] [serial?] KASAN: slab-use-after-free Write in tty_init_dev 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" syzbot has found a reproducer for the following issue on: HEAD commit: bc35965f6940 Merge tag 'mm-hotfixes-stable-2026-09-03-17-4.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=11f508f9580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f dashboard link: https://syzkaller.appspot.com/bug?extid=fe63e4d633540f230624 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b638f9580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+fe63e4d633540f230624@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-use-after-free in tty_init_dev.part.0+0x44f/0x470 drivers/tty/tty_io.c:1397 Write of size 8 at addr ffff888039c5f128 by task syz-executor411/6004 CPU: 2 UID: 0 PID: 6004 Comm: syz-executor411 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 tty_init_dev.part.0+0x44f/0x470 drivers/tty/tty_io.c:1397 tty_init_dev include/linux/err.h:78 [inline] tty_open_by_driver drivers/tty/tty_io.c:2046 [inline] tty_open+0x953/0xe20 drivers/tty/tty_io.c:2093 chrdev_open+0x234/0x6a0 fs/char_dev.c:411 do_dentry_open+0x6ab/0x14d0 fs/open.c:996 vfs_open+0x82/0x3f0 fs/open.c:1101 do_open fs/namei.c:4837 [inline] path_openat+0x19fa/0x2440 fs/namei.c:5000 do_file_open+0x20e/0x430 fs/namei.c:5029 do_sys_openat2+0x10f/0x1e0 fs/open.c:1417 do_sys_open fs/open.c:1423 [inline] __do_sys_openat fs/open.c:1439 [inline] __se_sys_openat fs/open.c:1434 [inline] __x64_sys_openat+0x12d/0x210 fs/open.c:1434 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd79f471dde Code: 08 0f 85 f5 e2 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 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08 RSP: 002b:00007fd79f41c158 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007fd79f41c6c0 RCX: 00007fd79f471dde RDX: 0000000000000102 RSI: 00007fd79f4c11a3 RDI: ffffffffffffff9c RBP: 0000000000000021 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffd0 R13: 0000000000000010 R14: 00007ffe14e7e850 R15: 00007ffe14e7e938 Allocated by task 5997: 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+0x2f8/0x6d0 mm/slub.c:5563 _kmalloc_noprof include/linux/slab.h:991 [inline] _kzalloc_noprof include/linux/slab.h:1312 [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 gser_alloc_inst+0x86/0x100 drivers/usb/gadget/function/f_serial.c:325 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+0x525/0xd40 fs/configfs/dir.c:1360 vfs_mkdir+0x364/0x850 fs/namei.c:5410 filename_mkdirat+0x48b/0x5e0 fs/namei.c:5443 __do_sys_mkdir fs/namei.c:5470 [inline] __se_sys_mkdir fs/namei.c:5467 [inline] __x64_sys_mkdir+0x6b/0x90 fs/namei.c:5467 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 6005: 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:2748 [inline] slab_free mm/slub.c:6499 [inline] kfree+0x22b/0x6d0 mm/slub.c:6792 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 gser_free_inst+0x3b/0x50 drivers/usb/gadget/function/f_serial.c:311 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:5515 [inline] vfs_rmdir+0x328/0x8a0 fs/namei.c:5488 filename_rmdir+0x31a/0x5c0 fs/namei.c:5572 __do_sys_rmdir fs/namei.c:5595 [inline] __se_sys_rmdir fs/namei.c:5592 [inline] __x64_sys_rmdir+0x46/0x70 fs/namei.c:5592 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff888039c5f000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 296 bytes inside of freed 2048-byte region [ffff888039c5f000, ffff888039c5f800) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888039c5b000 pfn:0x39c58 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 ffff88801c042f00 ffffea00011fe010 ffffea0000d4be10 raw: ffff888039c5b000 0000000000080007 00000000f5000000 0000000000000000 head: 00fff00000000240 ffff88801c042f00 ffffea00011fe010 ffffea0000d4be10 head: ffff888039c5b000 0000000000080007 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5536, tgid 5536 (getty), ts 27613485294 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871 prep_new_page mm/page_alloc.c:1879 [inline] get_page_from_freelist+0x110d/0x35d0 mm/page_alloc.c:3943 __alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436 alloc_slab_page mm/slub.c:3347 [inline] allocate_slab mm/slub.c:3462 [inline] new_slab+0xa9/0x6e0 mm/slub.c:3513 refill_objects+0xe3/0x410 mm/slub.c:7410 refill_sheaf mm/slub.c:2885 [inline] __pcs_replace_empty_main+0x35e/0x650 mm/slub.c:4774 alloc_from_pcs mm/slub.c:4850 [inline] slab_alloc_node mm/slub.c:4984 [inline] __do_kmalloc_node mm/slub.c:5413 [inline] __kmalloc_node_track_caller_noprof+0x6a8/0x870 mm/slub.c:5545 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] nlmsg_new include/net/netlink.h:1055 [inline] audit_buffer_alloc kernel/audit.c:1846 [inline] audit_log_start+0x350/0x930 kernel/audit.c:1965 common_lsm_audit+0xb2/0x2b0 security/lsm_audit.c:442 slow_avc_audit+0x186/0x210 security/selinux/avc.c:778 avc_audit security/selinux/include/avc.h:131 [inline] avc_has_perm+0x1a6/0x1e0 security/selinux/avc.c:1197 inode_has_perm+0x166/0x1d0 security/selinux/hooks.c:1694 __file_has_perm+0x39c/0x460 security/selinux/hooks.c:1800 file_has_perm security/selinux/hooks.c:1816 [inline] selinux_file_fcntl+0x111/0x170 security/selinux/hooks.c:4212 page last free pid 5536 tgid 5536 ts 27612066419 stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] __free_pages_prepare mm/page_alloc.c:1418 [inline] __free_frozen_pages+0x79f/0x10f0 mm/page_alloc.c:2962 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:4683 [inline] slab_alloc_node mm/slub.c:4996 [inline] __do_kmalloc_node mm/slub.c:5413 [inline] __kmalloc_noprof+0x2cc/0x840 mm/slub.c:5439 _kmalloc_noprof include/linux/slab.h:995 [inline] tomoyo_add_entry security/tomoyo/common.c:2166 [inline] tomoyo_supervisor+0x65d/0x1340 security/tomoyo/common.c:2238 tomoyo_audit_path_number_log security/tomoyo/file.c:239 [inline] tomoyo_path_number_perm+0x445/0x580 security/tomoyo/file.c:739 tomoyo_path_chown+0x14b/0x1b0 security/tomoyo/tomoyo.c:384 security_path_chown+0x12a/0x2d0 security/security.c:1598 chown_common+0x3da/0x6e0 fs/open.c:820 vfs_fchown fs/open.c:890 [inline] vfs_fchown+0xcd/0x110 fs/open.c:882 ksys_fchown fs/open.c:902 [inline] __do_sys_fchown fs/open.c:907 [inline] __se_sys_fchown fs/open.c:905 [inline] __x64_sys_fchown+0xad/0x130 fs/open.c:905 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff888039c5f000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888039c5f080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888039c5f100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888039c5f180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888039c5f200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== --- 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.