From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f199.google.com (mail-oi1-f199.google.com [209.85.167.199]) (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 A5E1A3E3D9E for ; Fri, 16 Oct 2026 07:34:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792136069; cv=none; b=nrjtuD3VdjLlhjr3NuFD47vgmMK7a1OX0Bmg4+qHspCDlROAJlleFgyO3UK9NMDqVpP9ci87SgkvMl6YXUfdGJ2y1uwQe1zh7DPR7wx2m5tf6gWrTRJRhhdRkjhOJxT1BPXBe4sgKdHWAWIAByiVVTt71auzCi9Ikx8hS0zCPuQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792136069; c=relaxed/simple; bh=q5iUIWYW60cM0WPc202uqylYv2vTuJJuuMZPkex0ZoE=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=kf/UXGwwPZNrPbnd3nBSE6/knQR3l+ATawmTO0G72kKGI7FdWmTHnLS1R0VjsgRs1eEV4bPTd7xKabLlV1qumUcU8rrjlTOJeRELyrh2pU214jEmZbduLLhxTFp+CMwsqOqdJiBTRQEi5MuVis8xelbFBlq36JLzmtJZyWpLhK8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.167.199 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-f199.google.com with SMTP id 5614622812f47-4c467e19391so3720985b6e.3 for ; Fri, 16 Oct 2026 00:34:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792136066; x=1792740866; h=content-type:to:from:subject:message-id:in-reply-to:date :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=vM8+w6Df5oEiHBh7R/MMipDoTjRKtXIVMaP7vz7w6E4=; b=TqKZATommq5lpRzBzi/gOwskw41dGbE/dRkks2uef7Nge7E1YvQHpxw2Bokuj8OY/6 awL4Ekg+7sDEzw6UVQaig09HdZKKYzWwSbSBVnsZijB3SapRg4NiqW3qjWTyQhQXNLhR N+DCW+SJXfTsJzyaIO9abotWkCbG38pOJsLJUq5+EK158nmPA4QMJnqm8OSOsxOUK0Wq 27NJChkWbhTKrTsKUZvBWdoc5Osaea1ulO95EAP+VIiVo9TQ7HfySPVgIwMOaGZgg4v7 0pJstJcrAw7NfPDY5JzA161meMFWjRHq7AN+fse13WgWEu9sK+gNUJE7XjkgAnmlpdoo grZQ== X-Forwarded-Encrypted: i=1; AKwUvBwojR1DssU+v4LG8CVQsDrTSBMt7Vk2xywPblgbKkC93HThxgz7Vnm5NSDgCmmtEjF9ShD1+oJU9UbHhluz@vger.kernel.org X-Gm-Message-State: AFq9FYLKlMKCYJqnC5qsXNaY7plua3qbL73MMlfYH9HfUoLGIYT4IztV LejM85qpo13UoGltcPyWfYMlPJj6gCriTF5ZRg8xKCvpXg6SzCiPLsTUWhB7a/AaO5mCS13xI6G 8/obJm+JHvc6OtM7KPyyW16ukTGhRmVifUQC4dBd3fS6K/X5ad5pvK+ON6xc= Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:198c:b0:4e6:cc78:edc1 with SMTP id 5614622812f47-50c57b6e78bmr19127706b6e.42.1792136066417; Fri, 16 Oct 2026 00:34:26 -0700 (PDT) Date: Fri, 16 Oct 2026 00:34:26 -0700 In-Reply-To: <6a83a769.4d75e56a.c9a88.0007.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ad1d382.7952420f.283480.021e.GAE@google.com> Subject: Re: [syzbot] [fs?] possible deadlock in uvcg_extension_bm_controls_store From: syzbot To: a.hindborg@kernel.org, leitao@debian.org, linux-fsdevel@vger.kernel.org, linux-kernel@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: 2f2f7eeef8b0 Merge tag 'soc-fixes-7.3-3' of git://git.kern.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=17d6dfd1580000 kernel config: https://syzkaller.appspot.com/x/.config?x=c4b098695335c89f dashboard link: https://syzkaller.appspot.com/bug?extid=300213c2b5b55c0244f4 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1394be8e580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+300213c2b5b55c0244f4@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz-executor184/5998 is trying to acquire lock: ffffffff90c14b28 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_extension_bm_controls_store+0xe4/0xb00 drivers/usb/gadget/function/uvc_configfs.c:1125 but task is already holding lock: ffff888028accd70 (&p->frag_sem){++++}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline] ffff888028accd70 (&p->frag_sem){++++}-{4:4}, at: configfs_write_iter+0x238/0x430 fs/configfs/file.c:229 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&p->frag_sem){++++}-{4:4}: down_write_killable+0xa6/0x240 kernel/locking/rwsem.c:1643 configfs_rmdir+0x3b0/0x950 fs/configfs/dir.c:1543 vfs_rmdir+0x3e6/0x6a0 fs/namei.c:5544 filename_rmdir+0x292/0x520 fs/namei.c:5601 __do_sys_rmdir fs/namei.c:5624 [inline] __se_sys_rmdir+0x2e/0x140 fs/namei.c:5621 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (&sb->s_type->i_mutex_key#25){++++}-{4:4}: down_write+0x96/0x200 kernel/locking/rwsem.c:1631 inode_lock include/linux/fs.h:1024 [inline] configfs_depend_item_unlocked+0x153/0x420 fs/configfs/dir.c:1268 usbg_make_tpg+0x1e0/0x550 drivers/usb/gadget/function/f_tcm.c:1692 target_fabric_make_tpg+0xa8/0x6d0 drivers/target/target_core_fabric_configfs.c:947 configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1369 vfs_mkdir+0x40c/0x620 fs/namei.c:5439 filename_mkdirat+0x285/0x510 fs/namei.c:5472 __do_sys_mkdir fs/namei.c:5499 [inline] __se_sys_mkdir+0x34/0x150 fs/namei.c:5496 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (tpg_instances_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 tcm_alloc_inst+0x65/0x1a0 drivers/usb/gadget/function/f_tcm.c:2687 try_get_usb_function_instance drivers/usb/gadget/functions.c:28 [inline] usb_get_function_instance+0xe3/0x2f0 drivers/usb/gadget/functions.c:44 function_make+0x127/0x360 drivers/usb/gadget/configfs.c:626 configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1369 vfs_mkdir+0x40c/0x620 fs/namei.c:5439 filename_mkdirat+0x285/0x510 fs/namei.c:5472 __do_sys_mkdir fs/namei.c:5499 [inline] __se_sys_mkdir+0x34/0x150 fs/namei.c:5496 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (func_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 try_get_usb_function_instance drivers/usb/gadget/functions.c:18 [inline] usb_get_function_instance+0x2e/0x2f0 drivers/usb/gadget/functions.c:44 function_make+0x127/0x360 drivers/usb/gadget/configfs.c:626 configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1369 vfs_mkdir+0x40c/0x620 fs/namei.c:5439 filename_mkdirat+0x285/0x510 fs/namei.c:5472 __do_sys_mkdir fs/namei.c:5499 [inline] __se_sys_mkdir+0x34/0x150 fs/namei.c:5496 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (gadget_subsys.su_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 uvcg_extension_bm_controls_store+0xe4/0xb00 drivers/usb/gadget/function/uvc_configfs.c:1125 flush_write_buffer fs/configfs/file.c:207 [inline] configfs_write_iter+0x337/0x430 fs/configfs/file.c:229 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x612/0xba0 fs/read_write.c:687 ksys_write+0x150/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: gadget_subsys.su_mutex --> &sb->s_type->i_mutex_key#25 --> &p->frag_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&p->frag_sem); lock(&sb->s_type->i_mutex_key#25); lock(&p->frag_sem); lock(gadget_subsys.su_mutex); *** DEADLOCK *** locks held by syz-executor184/5998: 3, last CPU#1: #0: ffff88801e7d8460 (sb_writers#12){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2756 [inline] #0: ffff88801e7d8460 (sb_writers#12){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0 fs/read_write.c:683 #1: ffff888070770c80 (&buffer->mutex){+.+.}-{4:4}, at: configfs_write_iter+0x7e/0x430 fs/configfs/file.c:226 #2: ffff888028accd70 (&p->frag_sem){++++}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline] #2: ffff888028accd70 (&p->frag_sem){++++}-{4:4}, at: configfs_write_iter+0x238/0x430 fs/configfs/file.c:229 stack backtrace: CPU: 1 UID: 0 PID: 5998 Comm: syz-executor184 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219 check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 uvcg_extension_bm_controls_store+0xe4/0xb00 drivers/usb/gadget/function/uvc_configfs.c:1125 flush_write_buffer fs/configfs/file.c:207 [inline] configfs_write_iter+0x337/0x430 fs/configfs/file.c:229 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x612/0xba0 fs/read_write.c:687 ksys_write+0x150/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa3e20116b7 Code: 48 89 fa 4c 89 df e8 98 1d 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007ffcaf360150 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 000055558f99e400 RCX: 00007fa3e20116b7 RDX: 0000000000000002 RSI: 00007fa3e204d174 RDI: 0000000000000003 RBP: 00007fa3e204fc38 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffcaf360230 R13: 000055558f99fdb0 R14: 000055558f99e3d8 R15: 000055558f9a7e4b --- 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.