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<6ad73531.5c73e770.1a06c9.0104.GAE@google.com> Subject: Re: [syzbot] [usb?] [fs?] possible deadlock in uvc_func_allow_link From: syzbot To: gregkh@linuxfoundation.org, linux-fsdevel@vger.kernel.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: f47d223627f8 Merge tag 'vfs-7.4-rc1.sync_close' of git://g.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=1475c831580000 kernel config: https://syzkaller.appspot.com/x/.config?x=897740d587b37862 dashboard link: https://syzkaller.appspot.com/bug?extid=8c0a48f6c8357c9da819 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1275c831580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+8c0a48f6c8357c9da819@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz-executor238/6025 is trying to acquire lock: ffffffff914019a8 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvc_func_allow_link+0x76/0x3f0 drivers/usb/gadget/function/uvc_configfs.c:3651 but task is already holding lock: ffff88802eca5b80 (&sb->s_type->i_mutex_key#25){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline] ffff88802eca5b80 (&sb->s_type->i_mutex_key#25){+.+.}-{4:4}, at: configfs_symlink+0x452/0x1340 fs/configfs/symlink.c:201 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&sb->s_type->i_mutex_key#25){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631 inode_lock include/linux/fs.h:1024 [inline] configfs_depend_item_unlocked+0xf3/0x6a0 fs/configfs/dir.c:1268 usbg_make_tpg+0x251/0x610 drivers/usb/gadget/function/f_tcm.c:1692 target_fabric_make_tpg+0xab/0x8c0 drivers/target/target_core_fabric_configfs.c:947 configfs_mkdir+0x525/0xd40 fs/configfs/dir.c:1369 vfs_mkdir+0x364/0x850 fs/namei.c:5420 filename_mkdirat+0x48b/0x5e0 fs/namei.c:5453 __do_sys_mkdir fs/namei.c:5480 [inline] __se_sys_mkdir fs/namei.c:5477 [inline] __x64_sys_mkdir+0x6b/0x90 fs/namei.c:5477 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (tpg_instances_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1c20 kernel/locking/mutex.c:821 tcm_alloc_inst+0x5f/0x1e0 drivers/usb/gadget/function/f_tcm.c:2687 try_get_usb_function_instance+0x136/0x1f0 drivers/usb/gadget/functions.c:28 usb_get_function_instance+0x16/0x70 drivers/usb/gadget/functions.c:44 function_make+0x18c/0x3f0 drivers/usb/gadget/configfs.c:626 configfs_mkdir+0x525/0xd40 fs/configfs/dir.c:1369 vfs_mkdir+0x364/0x850 fs/namei.c:5420 filename_mkdirat+0x48b/0x5e0 fs/namei.c:5453 __do_sys_mkdir fs/namei.c:5480 [inline] __se_sys_mkdir fs/namei.c:5477 [inline] __x64_sys_mkdir+0x6b/0x90 fs/namei.c:5477 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (func_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1c20 kernel/locking/mutex.c:821 try_get_usb_function_instance+0x26/0x1f0 drivers/usb/gadget/functions.c:18 usb_get_function_instance+0x16/0x70 drivers/usb/gadget/functions.c:44 function_make+0x18c/0x3f0 drivers/usb/gadget/configfs.c:626 configfs_mkdir+0x525/0xd40 fs/configfs/dir.c:1369 vfs_mkdir+0x364/0x850 fs/namei.c:5420 filename_mkdirat+0x48b/0x5e0 fs/namei.c:5453 __do_sys_mkdir fs/namei.c:5480 [inline] __se_sys_mkdir fs/namei.c:5477 [inline] __x64_sys_mkdir+0x6b/0x90 fs/namei.c:5477 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (gadget_subsys.su_mutex){+.+.}-{4:4}: check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209 check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1c20 kernel/locking/mutex.c:821 uvc_func_allow_link+0x76/0x3f0 drivers/usb/gadget/function/uvc_configfs.c:3651 configfs_symlink+0x695/0x1340 fs/configfs/symlink.c:211 vfs_symlink fs/namei.c:5804 [inline] vfs_symlink+0x178/0x4d0 fs/namei.c:5783 filename_symlinkat+0x2a6/0x560 fs/namei.c:5829 __do_sys_symlink fs/namei.c:5856 [inline] __se_sys_symlink fs/namei.c:5852 [inline] __x64_sys_symlink+0x79/0xb0 fs/namei.c:5852 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 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 --> tpg_instances_lock --> &sb->s_type->i_mutex_key#25 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sb->s_type->i_mutex_key#25); lock(tpg_instances_lock); lock(&sb->s_type->i_mutex_key#25); lock(gadget_subsys.su_mutex); *** DEADLOCK *** locks held by syz-executor238/6025: 2, last CPU#3: #0: ffff888025b44460 (sb_writers#13){.+.+}-{0:0}, at: filename_create+0x10d/0x400 fs/namei.c:5095 #1: ffff88802eca5b80 (&sb->s_type->i_mutex_key#25){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline] #1: ffff88802eca5b80 (&sb->s_type->i_mutex_key#25){+.+.}-{4:4}, at: configfs_symlink+0x452/0x1340 fs/configfs/symlink.c:201 stack backtrace: CPU: 3 UID: 0 PID: 6025 Comm: syz-executor238 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_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209 check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1c20 kernel/locking/mutex.c:821 uvc_func_allow_link+0x76/0x3f0 drivers/usb/gadget/function/uvc_configfs.c:3651 configfs_symlink+0x695/0x1340 fs/configfs/symlink.c:211 vfs_symlink fs/namei.c:5804 [inline] vfs_symlink+0x178/0x4d0 fs/namei.c:5783 filename_symlinkat+0x2a6/0x560 fs/namei.c:5829 __do_sys_symlink fs/namei.c:5856 [inline] __se_sys_symlink fs/namei.c:5852 [inline] __x64_sys_symlink+0x79/0xb0 fs/namei.c:5852 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f17e04c5357 Code: 77 01 c3 48 c7 c2 d8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 b8 58 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 d8 ff ff ff f7 d8 64 89 02 b8 RSP: 002b:00007ffdfd785e48 EFLAGS: 00000206 ORIG_RAX: 0000000000000058 RAX: ffffffffffffffda RBX: 00007f17e051e1e8 RCX: 00007f17e04c5357 RDX: 0000000000000000 RSI: 00007f17e051e170 RDI: 00007f17e051e1e8 RBP: 00007f17e051e300 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: 00007f17e051e250 R13: 00007f17e051e298 R14: 00007f17e051e2d8 R15: 00007f17e051e1b0 --- 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.