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AHgh+RpNjP2rzEAdT7RxkEC/w8vVgk0Ag18RMfASlBYqlpBIbLgj005BfWdzowqrYBGJCb+LF1d+PCX2t1MMlw4=@vger.kernel.org X-Gm-Message-State: AOJu0YwVtgaV12mHHfjocRvWZAgfzR9QOFMLUGDW4qkLz+vmzJRWsMdp 7rjnWz1m61fqItK8ukcNX3MQ7MYNzRULHRQrGXIGw5JN5yRboWou8odYgSkHJq/QuO+oa04S1bS UY/P8ka6AyG1kPCTvsoR4Y/sUtXzCFQqCmxat3SN4SO4C/05t820VWKncq2g= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:6ac2:b0:6ae:901e:b312 with SMTP id 006d021491bc7-6ae97005448mr2698301eaf.29.1785917543338; Wed, 05 Aug 2026 01:12:23 -0700 (PDT) Date: Wed, 05 Aug 2026 01:12:23 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a72f067.13623e66.bdc14.0055.GAE@google.com> Subject: [syzbot] [overlayfs?] possible deadlock in mnt_want_write (9) From: syzbot To: a.hindborg@kernel.org, amir73il@gmail.com, leitao@debian.org, linux-kernel@vger.kernel.org, linux-unionfs@vger.kernel.org, miklos@szeredi.hu, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: cc2b5f627e8c Add linux-next specific files for 20260714 git tree: linux-next console+strace: https://syzkaller.appspot.com/x/log.txt?x=13631e32580000 kernel config: https://syzkaller.appspot.com/x/.config?x=2290ccbf984c524f dashboard link: https://syzkaller.appspot.com/bug?extid=da381387152f0dd8bedf compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11178db9580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16b2f4c6580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/6836f8efb1da/disk-cc2b5f62.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/0109d3477cc7/vmlinux-cc2b5f62.xz kernel image: https://storage.googleapis.com/syzbot-assets/c2e49e350bbf/bzImage-cc2b5f62.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+da381387152f0dd8bedf@syzkaller.appspotmail.com Mass Storage Function, version: 2009/09/11 LUN: removable file: (no medium) ============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz-executor262/5614 is trying to acquire lock: ffff88801dfd2510 (sb_writers#8){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:494 but task is already holding lock: ffff88801dfd2510 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline] ffff88801dfd2510 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(sb_writers#8); lock(sb_writers#8); *** DEADLOCK *** May be due to missing lock nesting notation locks held by syz-executor262/5614: 4, last CPU#1: #0: ffff88801dfd2510 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline] #0: ffff88801dfd2510 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683 #1: ffff888028861a78 (&buffer->mutex){+.+.}-{4:4}, at: configfs_write_iter+0x81/0x430 fs/configfs/file.c:226 #2: ffff888033abd068 (&p->frag_sem){.+.+}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline] #2: ffff888033abd068 (&p->frag_sem){.+.+}-{4:4}, at: configfs_write_iter+0x23b/0x430 fs/configfs/file.c:229 #3: ffff888038383998 (&common->filesem){+.+.}-{4:4}, at: fsg_store_file+0x163/0x400 drivers/usb/gadget/function/storage_common.c:452 stack backtrace: CPU: 1 UID: 0 PID: 5614 Comm: syz-executor262 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_deadlock_bug+0x27a/0x290 kernel/locking/lockdep.c:3057 check_deadlock kernel/locking/lockdep.c:3109 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x261c/0x2e40 kernel/locking/lockdep.c:5254 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906 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+0x4d/0x1c0 include/linux/fs/super.h:125 mnt_want_write+0x41/0x90 fs/namespace.c:494 open_last_lookups fs/namei.c:4591 [inline] path_openat+0xa7b/0x3850 fs/namei.c:4854 do_file_open+0x23e/0x4a0 fs/namei.c:4886 file_open_name fs/open.c:1326 [inline] filp_open+0x16d/0x1d0 fs/open.c:1343 fsg_lun_open+0x6c/0xe00 drivers/usb/gadget/function/storage_common.c:194 fsg_store_file+0x19e/0x400 drivers/usb/gadget/function/storage_common.c:455 flush_write_buffer fs/configfs/file.c:207 [inline] configfs_write_iter+0x33a/0x430 fs/configfs/file.c:229 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x61e/0xbb0 fs/read_write.c:687 ksys_write+0x156/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f79667de649 Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe39c70488 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000200000000100 RCX: 00007f79667de649 RDX: 0000000000000002 RSI: 0000200000000f00 RDI: 0000000000000003 RBP: 69666e6f635f796d R08: 0000000000000006 R09: 0000000000000006 R10: 0000000000000006 R11: 0000000000000246 R12: 00007ffe39c705f8 R13: 0000200000000108 R14: 00007f7966871c40 R15: 0000000000000002 mass_storage.usb0/lun.0: unable to open backing file: fi --- 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