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AKwUvBwzlHWGC6lJcTnMlXymI3hjDBJ1D3N6DPt0sij2kd50K/JXwpKWleCQlQKfsd6EplUHgCAUwhHKjLdMO6k=@vger.kernel.org X-Gm-Message-State: AFuF++nztQFlRrBr2qsEJTmYxzYhIEEVCfA5WCV/8hPdACJLug7sJPsr KvPQb105srh8gvGEhe+URuXjgVbkKBWSzDfgApv8J1yUAQYAzpuk5HFOwbPUdv2ibenwcYQ9mFU GNsUsn9eKhv+ADWFo0tAAJnU5oHNNSN7uS5KLXis2I0nF96vdJqhl+wi4/Nc= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:1642:b0:4d6:9133:cfe0 with SMTP id 5614622812f47-4d72cd32638mr3804097b6e.37.1790323354036; Fri, 25 Sep 2026 01:02:34 -0700 (PDT) Date: Fri, 25 Sep 2026 01:02:34 -0700 In-Reply-To: <6a895324.ae6ddae5.3da009.0053.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ab62a9a.7eec07f4.c25c.0004.GAE@google.com> Subject: Re: [syzbot] [usb?] possible deadlock in lookup_open From: syzbot To: a.hindborg@kernel.org, gregkh@linuxfoundation.org, leitao@debian.org, linux-kernel@vger.kernel.org, linux-usb@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: 5fc5768c7ca9 Merge tag 'bpf-fixes' of git://git.kernel.org.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=15a7a2c9580000 kernel config: https://syzkaller.appspot.com/x/.config?x=2a820d8842c77560 dashboard link: https://syzkaller.appspot.com/bug?extid=c39ae720fb00e7e6f14b compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 userspace arch: i386 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1562fc05580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1409ed25580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-5fc5768c.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/2038b7f58a0e/vmlinux-5fc5768c.xz kernel image: https://storage.googleapis.com/syzbot-assets/1f03bad44e45/bzImage-5fc5768c.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+c39ae720fb00e7e6f14b@syzkaller.appspotmail.com LUN: removable file: (no medium) ============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.0.17/5921 is trying to acquire lock: ffff888022716460 (sb_writers#12){.+.+}-{0:0}, at: lookup_open+0x150/0x1990 fs/namei.c:4451 but task is already holding lock: ffff888022716460 (sb_writers#12){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(sb_writers#12); lock(sb_writers#12); *** DEADLOCK *** May be due to missing lock nesting notation locks held by syz.0.17/5921: 4, last CPU#1: #0: ffff888022716460 (sb_writers#12){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739 #1: ffff88802a22f280 (&buffer->mutex){+.+.}-{4:4}, at: configfs_write_iter+0x76/0x4e0 fs/configfs/file.c:226 #2: ffff888023773970 (&p->frag_sem){.+.+}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline] #2: ffff888023773970 (&p->frag_sem){.+.+}-{4:4}, at: configfs_write_iter+0x218/0x4e0 fs/configfs/file.c:229 #3: ffff888024051120 (&common->filesem){+.+.}-{4:4}, at: fsg_store_file+0x193/0x450 drivers/usb/gadget/function/storage_common.c:452 stack backtrace: CPU: 1 UID: 0 PID: 5921 Comm: syz.0.17 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_deadlock_bug.cold+0xbd/0xca kernel/locking/lockdep.c:3085 check_deadlock kernel/locking/lockdep.c:3137 [inline] validate_chain kernel/locking/lockdep.c:3939 [inline] __lock_acquire+0x13f4/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline] __sb_start_write include/linux/fs/super.h:19 [inline] sb_start_write include/linux/fs/super.h:125 [inline] mnt_want_write+0x6f/0x420 fs/namespace.c:494 lookup_open+0x150/0x1990 fs/namei.c:4451 open_last_lookups fs/namei.c:4767 [inline] path_openat+0xa2c/0x2440 fs/namei.c:4997 do_file_open+0x20e/0x430 fs/namei.c:5029 file_open_name+0x1c3/0x3e0 fs/open.c:1375 filp_open+0x2e/0x50 fs/open.c:1392 fsg_lun_open+0x6b/0x7b0 drivers/usb/gadget/function/storage_common.c:194 fsg_store_file+0x1e7/0x450 drivers/usb/gadget/function/storage_common.c:455 flush_write_buffer fs/configfs/file.c:207 [inline] configfs_write_iter+0x302/0x4e0 fs/configfs/file.c:229 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6af/0x1050 fs/read_write.c:687 ksys_write+0x12a/0x250 fs/read_write.c:739 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline] __do_fast_syscall_32+0x13a/0x8b0 arch/x86/entry/syscall_32.c:291 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:316 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf701efec Code: Unable to access opcode bytes at 0xf701efc2. RSP: 002b:00000000ff91c89c EFLAGS: 00000292 ORIG_RAX: 0000000000000004 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000800003c0 RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 mass_storage.0/lun.0: unable to open backing file: file0 --- 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.