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<6af922a4.097d52ff.3d440.0011.GAE@google.com> Subject: Re: [syzbot] [usb?] possible deadlock in uvcg_extension_ba_source_id_show From: syzbot To: gregkh@linuxfoundation.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: aacb77975041 Merge tag 'ovl-fixes-7.4-rc3' of git://git.ke.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=11cd29ad580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1cf189394a856f11 dashboard link: https://syzkaller.appspot.com/bug?extid=caf0e2bd08dda787005d 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=15cd29ad580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+caf0e2bd08dda787005d@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz-executor339/5973 is trying to acquire lock: ffffffff916376e8 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_extension_ba_source_id_show+0x7c/0x310 drivers/usb/gadget/function/uvc_configfs.c:1018 but task is already holding lock: ffff8880242aa370 (&p->frag_sem){++++}-{4:4}, at: fill_read_buffer fs/configfs/file.c:66 [inline] ffff8880242aa370 (&p->frag_sem){++++}-{4:4}, at: configfs_read_iter+0x346/0x6f0 fs/configfs/file.c:88 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&p->frag_sem){++++}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 down_write_killable+0x8e/0x240 kernel/locking/rwsem.c:1643 configfs_rmdir+0x3fa/0x950 fs/configfs/dir.c:1543 vfs_rmdir fs/namei.c:5533 [inline] vfs_rmdir+0x328/0x8e0 fs/namei.c:5506 filename_rmdir+0x31a/0x610 fs/namei.c:5590 __do_sys_rmdir fs/namei.c:5613 [inline] __se_sys_rmdir fs/namei.c:5610 [inline] __x64_sys_rmdir+0x46/0x70 fs/namei.c:5610 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (&sb->s_type->i_mutex_key#24){++++}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 down_write+0x86/0x1f0 kernel/locking/rwsem.c:1631 inode_lock include/linux/fs.h:1027 [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+0x36d/0x8a0 fs/namei.c:5428 filename_mkdirat+0x4c4/0x630 fs/namei.c:5461 __do_sys_mkdir fs/namei.c:5488 [inline] __se_sys_mkdir fs/namei.c:5485 [inline] __x64_sys_mkdir+0x6b/0x90 fs/namei.c:5485 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 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+0x19f/0x1c10 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+0x36d/0x8a0 fs/namei.c:5428 filename_mkdirat+0x4c4/0x630 fs/namei.c:5461 __do_sys_mkdir fs/namei.c:5488 [inline] __se_sys_mkdir fs/namei.c:5485 [inline] __x64_sys_mkdir+0x6b/0x90 fs/namei.c:5485 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 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+0x19f/0x1c10 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+0x36d/0x8a0 fs/namei.c:5428 filename_mkdirat+0x4c4/0x630 fs/namei.c:5461 __do_sys_mkdir fs/namei.c:5488 [inline] __se_sys_mkdir fs/namei.c:5485 [inline] __x64_sys_mkdir+0x6b/0x90 fs/namei.c:5485 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 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+0x19f/0x1c10 kernel/locking/mutex.c:821 uvcg_extension_ba_source_id_show+0x7c/0x310 drivers/usb/gadget/function/uvc_configfs.c:1018 fill_read_buffer fs/configfs/file.c:68 [inline] configfs_read_iter+0x426/0x6f0 fs/configfs/file.c:88 new_sync_read fs/read_write.c:473 [inline] vfs_read+0x825/0xb30 fs/read_write.c:554 ksys_read+0x12a/0x250 fs/read_write.c:696 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 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#24 --> &p->frag_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&p->frag_sem); lock(&sb->s_type->i_mutex_key#24); lock(&p->frag_sem); lock(gadget_subsys.su_mutex); *** DEADLOCK *** locks held by syz-executor339/5973: 2, on CPU#1: #0: ffff88807364f680 (&buffer->mutex){+.+.}-{4:4}, at: configfs_read_iter+0x79/0x6f0 fs/configfs/file.c:86 #1: ffff8880242aa370 (&p->frag_sem){++++}-{4:4}, at: fill_read_buffer fs/configfs/file.c:66 [inline] #1: ffff8880242aa370 (&p->frag_sem){++++}-{4:4}, at: configfs_read_iter+0x346/0x6f0 fs/configfs/file.c:88 stack backtrace: CPU: 1 UID: 0 PID: 5973 Comm: syz-executor339 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 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+0x19f/0x1c10 kernel/locking/mutex.c:821 uvcg_extension_ba_source_id_show+0x7c/0x310 drivers/usb/gadget/function/uvc_configfs.c:1018 fill_read_buffer fs/configfs/file.c:68 [inline] configfs_read_iter+0x426/0x6f0 fs/configfs/file.c:88 new_sync_read fs/read_write.c:473 [inline] vfs_read+0x825/0xb30 fs/read_write.c:554 ksys_read+0x12a/0x250 fs/read_write.c:696 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fb9d4bb53f7 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:00007ffd83b44e50 EFLAGS: 00000202 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 000055555f71e400 RCX: 00007fb9d4bb53f7 RDX: 0000000000000080 RSI: 00007ffd83b44ea0 RDI: 0000000000000003 RBP: 00007fb9d4beb708 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007fb9d4bef01a R13: 000055555f71f813 R14: 00007fb9d4beb130 R15: 0000000000000002