From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.167.200 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794761196; b=yokCX+APilqY5hZA9LthXEW6nX5ne8N8kFnt0F879PoAfZMlwhV6894UI0a7IuPgw58G QnxdtMFrRfvMz4nKoHjlR9dRs0uhS22wWyGy2sd0BcYCiBt4EIIS/FcU0Er1CNVDpiD41 N0tZqPv9496OC+2GXqgW5ct/nOAKcxCKyWlOGhPmriu6wL06+nMV/GuE+Ss0b2rRRqG7l PoGqS4QcaS1FqYlgPudmhPHnmir+samThNOg2egKbSkDLxyFVzyIXRQeLTkrY4fgqod2X 42pFMv8TljuRW4FnUANF4cvnljCeSmkUWNBwX5EibDyJAkcKxLKAOlwUJJVgDob/X1g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794761196; h=DMARC-Filter:Received:X-Google-DKIM-Signature:X-Forwarded-Encrypted: X-Gm-Message-State:MIME-Version:X-Received:Date: X-Google-Appengine-App-Id:X-Google-Appengine-App-Id-Alias:Message-ID: Subject:From:To:Content-Type; bh=IigkRWKWr+odYFJBZzviN42v67VY7zEQS2aC4gMD2vM=; b=xOsHAeJSwmIFWqJhU3VcEss0oqYAma9MemXBXRhTGxXbhsCSynIFNXFYDU13TB1Vi+a1 m8599e1UNUVIWEfYY9eP5+tUifMOw7subEjd118qCN9BRa5TZFVxCE0hXfO3sDCvCHhy8 S80TtybVT9oPtsyczpC8DyZcvu5nnPjmNOmXgoa3qbwoHcGaPHWGpMbqZwCILvf8E0CII 9Jk9GDk0kHWO509r6Gp2Lx3ajzYAKQqlb3Pz6omUgMt/nEmS9OpQpuQJ9BToC+vlk0EDC d9Cm/pFdfcR71Rdy2dfnwZK7V0yphpeooFPcTPP5QK4uAMy3FIqw34wj6QsXY/awsnQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.remote-ip=209.85.167.200 Received: from mail-oi1-f200.google.com (mail-oi1-f200.google.com [209.85.167.200]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EE058606A31E for ; Sun, 15 Nov 2026 16:46:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org EE058606A31E Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oi1-f200.google.com with SMTP id 5614622812f47-4a7de733fa9so3372096b6e.3 for ; Sun, 15 Nov 2026 08:46:35 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1794761195; x=1795365995; h=content-type:to:from:subject:message-id:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=IigkRWKWr+odYFJBZzviN42v67VY7zEQS2aC4gMD2vM=; b=ZBnyx26DHwuDck+bgyumwwtlDeK6+bTqw63qMEp2SYmxNnecvYuJeSIXOOYoJPLQxP HOAXZeYFEzc3UZA7koy/YAeg4dSvSzcGgftB69oOF45xhkkeBq/jtvpLM60ojIpvlSP4 7KLK5H09raXSS+lpnc2buolr1z5h7S2FJDwRgjSexu/Iu2I9qSrQ4Dwu1/ayA4YbScUo RutqXpB4hcWx1RjJkrv0Yoqz+fQQbjNW+E8rgg3DFNCad9sTsJRmaKEod2BQqt4CziDH M7QQGZYqkWjWZZKx/3EjEMdCR3TQJRG7RSt3scC8+2RmDZRJVM0hYE8gTfXaUOjDmc6h Ir1g== X-Forwarded-Encrypted: i=1; AL+hErH+bmI/yWHtJa1uz7TDN4Pij2qhf7qyixrtbj7zpA3nH9XDAxxtTrJUaApx24nEcIQEVJHRuzQjvXDysIM9@vger.kernel.org X-Gm-Message-State: APuU4Z/DW6OFYG09grbnbsDP9QD8C5kudt4tU/zffmjcGWFmFnQWdSjL AJwnM5cktiREAtHVIrXkTR/6nSeAwQlAkES7yG8cVtyrDl/5s/CPa8KBZS1HXJjbhWaOoqYeV+g 6njZ+3d+4z4TsGL5XQrwNEudzexorGN5w0FULHHtC3methwlcw0HmnuwRZ4w= X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-Received: by 2002:a05:6809:211:10b0:571:7f0f:924a with SMTP id 5614622812f47-5717f10b319mr3300396b6e.35.1794761195052; Sun, 15 Nov 2026 08:46:35 -0800 (PST) Date: Sun, 15 Nov 2026 08:46:35 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6af9e1eb.920b2b3a.148c65.002f.GAE@google.com> Subject: [syzbot] [fs?] [driver-core?] KASAN: slab-use-after-free Read in cdev_put From: syzbot To: dakr@kernel.org, driver-core@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 2800868f6322 Merge tag 'sound-7.4-rc3' of git://git.kernel.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=1386fe4e580000 kernel config: https://syzkaller.appspot.com/x/.config?x=5c210800cfc8f61e dashboard link: https://syzkaller.appspot.com/bug?extid=667788430769ef9ddf25 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 userspace arch: i386 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11c4cb69580000 AI-generated root cause summary: In posix_clock_register() (kernel/time/posix-clock.c), clk->dev and clk->cdev.owner are assigned only after cdev_device_add(&clk->cdev, dev) returns. As soon as cdev_add() executes inside cdev_device_add(), the character device is live and can be opened by userspace. If posix_clock_open() runs in this window while clk->dev is still NULL, get_device(clk->dev) is a no-op and fails to acquire a reference on the device. When the file is later closed, posix_clock_release() calls put_device(clk->dev) on the now-initialized pointer, causing an unbalanced reference drop that prematurely frees the struct ptp_clock; subsequent invocation of cdev_put(inode->i_cdev) in __fput() then accesses the freed memory, causing a slab use-after-free. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=667788430769ef9ddf25 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+667788430769ef9ddf25@syzkaller.appspotmail.com ========================= ================================================================== BUG: KASAN: slab-use-after-free in cdev_put fs/char_dev.c:363 [inline] BUG: KASAN: slab-use-after-free in cdev_put+0x58/0x60 fs/char_dev.c:360 Read of size 8 at addr ffff888043a4a090 by task syz-executor804/6199 CPU: 2 UID: 0 PID: 6199 Comm: syz-executor804 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 cdev_put fs/char_dev.c:363 [inline] cdev_put+0x58/0x60 fs/char_dev.c:360 __fput+0x904/0xb50 fs/file_table.c:515 fput_close_sync+0x118/0x250 fs/file_table.c:618 filp_close_sync+0x75/0xa0 fs/open.c:1574 close_files fs/file.c:572 [inline] put_files_struct fs/file.c:584 [inline] put_files_struct+0x1f7/0x390 fs/file.c:581 switch_files_struct fs/file.c:598 [inline] exit_files+0x85/0xb0 fs/file.c:604 do_exit+0x896/0x2a00 kernel/exit.c:977 do_group_exit+0xd5/0x2a0 kernel/exit.c:1123 __do_sys_exit_group kernel/exit.c:1134 [inline] __se_sys_exit_group kernel/exit.c:1132 [inline] __ia32_sys_exit_group+0x3e/0x50 kernel/exit.c:1132 ia32_sys_call+0x1a39/0x1a40 arch/x86/include/generated/asm/syscalls_32.h:253 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline] __do_fast_syscall_32+0x14d/0x8e0 arch/x86/entry/syscall_32.c:286 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:311 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf7e91fbc Code: Unable to access opcode bytes at 0xf7e91f92. RSP: 002b:00000000f5e85688 EFLAGS: 00000292 ORIG_RAX: 00000000000000fc RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000ffffffe8 RDX: 00000000000000fc RSI: 00000000f5e856d0 RDI: 00000000f5e856d0 RBP: 00000000f5e856d0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Allocated by task 6126: 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:409 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:426 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x2f8/0x6d0 mm/slub.c:5680 _kmalloc_noprof include/linux/slab.h:991 [inline] _kzalloc_noprof include/linux/slab.h:1312 [inline] ptp_clock_register+0x187/0x1780 drivers/ptp/ptp_clock.c:343 ptp_vclock_register+0x51f/0xa10 drivers/ptp/ptp_vclock.c:256 n_vclocks_store+0x1b1/0x600 drivers/ptp/ptp_sysfs.c:230 dev_attr_store+0x58/0x80 drivers/base/core.c:2509 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:575 [inline] vfs_write+0x6af/0x1040 fs/read_write.c:667 ksys_pwrite64+0x113/0x230 fs/read_write.c:774 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline] do_int80_emulation+0x16a/0x670 arch/x86/entry/syscall_32.c:170 asm_int80_emulation+0x1a/0x20 arch/x86/include/asm/idtentry.h:598 Freed by task 6199: 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:264 [inline] __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:296 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2780 [inline] slab_free mm/slub.c:6630 [inline] kfree+0x22b/0x6d0 mm/slub.c:6923 device_release+0xd2/0x270 drivers/base/core.c:2640 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1f7/0x640 lib/kobject.c:737 put_device+0x1f/0x30 drivers/base/core.c:3886 posix_clock_release+0xd5/0x150 kernel/time/posix-clock.c:142 __fput+0x3fb/0xb50 fs/file_table.c:512 fput_close_sync+0x118/0x250 fs/file_table.c:618 filp_close_sync+0x75/0xa0 fs/open.c:1574 close_files fs/file.c:572 [inline] put_files_struct fs/file.c:584 [inline] put_files_struct+0x1f7/0x390 fs/file.c:581 switch_files_struct fs/file.c:598 [inline] exit_files+0x85/0xb0 fs/file.c:604 do_exit+0x896/0x2a00 kernel/exit.c:977 do_group_exit+0xd5/0x2a0 kernel/exit.c:1123 __do_sys_exit_group kernel/exit.c:1134 [inline] __se_sys_exit_group kernel/exit.c:1132 [inline] __ia32_sys_exit_group+0x3e/0x50 kernel/exit.c:1132 ia32_sys_call+0x1a39/0x1a40 arch/x86/include/generated/asm/syscalls_32.h:253 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline] __do_fast_syscall_32+0x14d/0x8e0 arch/x86/entry/syscall_32.c:286 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:311 entry_SYSENTER_compat_after_hwframe+0x84/0x8e The buggy address belongs to the object at ffff888043a4a000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 144 bytes inside of freed 4096-byte region [ffff888043a4a000, ffff888043a4b000) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x43a48 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 04fff00000000040 ffff88801d443040 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000 head: 04fff00000000040 ffff88801d443040 dead000000000122 0000000000000000 head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000 head: 04fff00000000003 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 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6143, tgid 6143 (udevd), ts 68631299502 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1860 prep_new_page mm/page_alloc.c:1868 [inline] get_page_from_freelist+0xdae/0x2c80 mm/page_alloc.c:3950 __alloc_frozen_pages_noprof+0x2ad/0x31e0 mm/page_alloc.c:5492 alloc_slab_page mm/slub.c:3384 [inline] allocate_slab mm/slub.c:3499 [inline] new_slab+0xb1/0x6d0 mm/slub.c:3550 refill_objects+0xe3/0x410 mm/slub.c:7539 refill_sheaf mm/slub.c:2917 [inline] __pcs_replace_empty_main+0x35e/0x650 mm/slub.c:4811 alloc_from_pcs mm/slub.c:4887 [inline] slab_alloc_node mm/slub.c:5021 [inline] __do_kmalloc_node mm/slub.c:5530 [inline] __kmalloc_noprof+0x677/0x840 mm/slub.c:5556 _kmalloc_noprof include/linux/slab.h:995 [inline] tomoyo_realpath_from_path+0xb6/0x690 security/tomoyo/realpath.c:251 tomoyo_get_realpath security/tomoyo/file.c:151 [inline] tomoyo_path_perm+0x276/0x460 security/tomoyo/file.c:827 tomoyo_path_unlink+0x91/0xe0 security/tomoyo/tomoyo.c:162 security_path_unlink+0x145/0x2b0 security/security.c:1498 filename_unlinkat+0x316/0x770 fs/namei.c:5734 __do_sys_unlink fs/namei.c:5772 [inline] __se_sys_unlink fs/namei.c:5769 [inline] __x64_sys_unlink+0x46/0x70 fs/namei.c:5769 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x780 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f page last free pid 5200 tgid 5200 ts 68611259383 stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] __free_pages_prepare mm/page_alloc.c:1402 [inline] __free_frozen_pages+0x7b1/0x10f0 mm/page_alloc.c:2958 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:361 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4720 [inline] slab_alloc_node mm/slub.c:5033 [inline] kmem_cache_alloc_lru_noprof+0x265/0x6a0 mm/slub.c:5066 shmem_alloc_inode+0x25/0x50 mm/shmem.c:5374 alloc_inode+0x68/0x250 fs/inode.c:338 new_inode+0x22/0x1c0 fs/inode.c:1192 __shmem_get_inode mm/shmem.c:3285 [inline] shmem_get_inode+0x1e3/0xff0 mm/shmem.c:3361 shmem_mknod+0x217/0x480 mm/shmem.c:4072 lookup_open+0xd8a/0x19e0 fs/namei.c:4575 open_last_lookups fs/namei.c:4774 [inline] path_openat+0xe75/0x23f0 fs/namei.c:5013 do_file_open+0x20e/0x430 fs/namei.c:5045 do_sys_openat2+0x163/0x1d0 fs/open.c:1443 do_sys_open fs/open.c:1449 [inline] __do_sys_openat fs/open.c:1465 [inline] __se_sys_openat fs/open.c:1460 [inline] __x64_sys_openat+0x12d/0x210 fs/open.c:1460 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x780 arch/x86/entry/syscall_64.c:89 Memory state around the buggy address: ffff888043a49f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888043a4a000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888043a4a080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888043a4a100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888043a4a180: 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 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