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AHgh+RrISYhffoNKM8uHYeyjihJq97k9XhtiAhzM0cfgh13xJOYiiucQQJFa2KZVSz6ZpfeEDg2RQuy2dyfJG3o=@vger.kernel.org X-Gm-Message-State: AOJu0Ywwt08nrmI379r9LmZ03RsciPIL+TLQ7fI1nU3KleXEeAm3mSw5 WueMjXwjxJ+cN4wbl9UqRLX1x5oDanboAnOF/1Cw9AP8Ki8sam03oPUGC2qIFjCTOxN/S+RGRlq 9mvoeSOPnxOTqsmTyMi7a5r7ybFZ8ESouriCzYTjyCi5Qt1N51Ism5Z1BHto= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:3448:b0:4a4:c12:ee68 with SMTP id 5614622812f47-4a4d01bb487mr8882354b6e.10.1784591787533; Mon, 20 Jul 2026 16:56:27 -0700 (PDT) Date: Mon, 20 Jul 2026 16:56:27 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a5eb5ab.42649fcc.6186.008b.GAE@google.com> Subject: [syzbot] [bluetooth?] KASAN: null-ptr-deref Read in l2cap_chan_hold_unless_zero From: syzbot To: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, luiz.dentz@gmail.com, marcel@holtmann.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: e22254e9ddd8 Merge tag 'xfs-fixes-7.2-rc4' of git://git.ke.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=13d46789580000 kernel config: https://syzkaller.appspot.com/x/.config?x=48ef5c5c0f192153 dashboard link: https://syzkaller.appspot.com/bug?extid=e6382a2f53f5fc7453ac 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=17b434b9580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17d46789580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-e22254e9.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/c69a30d7d78f/vmlinux-e22254e9.xz kernel image: https://storage.googleapis.com/syzbot-assets/f15a346cc7e1/bzImage-e22254e9.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+e6382a2f53f5fc7453ac@syzkaller.appspotmail.com ================================================================== BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:82 [inline] BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline] BUG: KASAN: null-ptr-deref in refcount_read include/linux/refcount.h:170 [inline] BUG: KASAN: null-ptr-deref in __refcount_add_not_zero include/linux/refcount.h:176 [inline] BUG: KASAN: null-ptr-deref in __refcount_inc_not_zero include/linux/refcount.h:317 [inline] BUG: KASAN: null-ptr-deref in refcount_inc_not_zero include/linux/refcount.h:335 [inline] BUG: KASAN: null-ptr-deref in kref_get_unless_zero include/linux/kref.h:133 [inline] BUG: KASAN: null-ptr-deref in l2cap_chan_hold_unless_zero+0x80/0x290 net/bluetooth/l2cap_core.c:511 Read of size 4 at addr 0000000000000008 by task syz.0.158/6397 CPU: 2 UID: 0 PID: 6397 Comm: syz.0.158 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 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] atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline] refcount_read include/linux/refcount.h:170 [inline] __refcount_add_not_zero include/linux/refcount.h:176 [inline] __refcount_inc_not_zero include/linux/refcount.h:317 [inline] refcount_inc_not_zero include/linux/refcount.h:335 [inline] kref_get_unless_zero include/linux/kref.h:133 [inline] l2cap_chan_hold_unless_zero+0x80/0x290 net/bluetooth/l2cap_core.c:511 l2cap_sock_cleanup_listen+0x8a/0x4d0 net/bluetooth/l2cap_sock.c:1535 l2cap_sock_release+0x69/0x280 net/bluetooth/l2cap_sock.c:1480 __sock_release+0xb3/0x260 net/socket.c:710 sock_close+0x1c/0x30 net/socket.c:1501 __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: 0033:0x7f3758d9de99 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:00007fff659f88f8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007f3759027da0 RCX: 00007f3758d9de99 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007f3759027da0 R08: 0000000000000006 R09: 0000000000000000 R10: 00007f3759027cb0 R11: 0000000000000246 R12: 0000000000046482 R13: 00007f375902609c R14: 00000000000461ac R15: 00007f3759026090 ================================================================== --- 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