On Thu, 1 Aug 2019, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 7f7867ff usb-fuzzer: main usb gadget fuzzer driver > git tree: https://github.com/google/kasan.git usb-fuzzer > console output: https://syzkaller.appspot.com/x/log.txt?x=136b6aec600000 > kernel config: https://syzkaller.appspot.com/x/.config?x=792eb47789f57810 > dashboard link: https://syzkaller.appspot.com/bug?extid=7bbcbe9c9ff0cd49592a > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+7bbcbe9c9ff0cd49592a@xxxxxxxxxxxxxxxxxxxxxxxxx > > ====================================================== > WARNING: possible circular locking dependency detected > 5.3.0-rc2+ #23 Not tainted > ------------------------------------------------------ > syz-executor.2/20386 is trying to acquire lock: > 00000000772249c6 (rio500_mutex){+.+.}, at: open_rio+0x16/0xc0 > drivers/usb/misc/rio500.c:64 > > but task is already holding lock: > 00000000d3e8f4b9 (minor_rwsem){++++}, at: usb_open+0x23/0x270 > drivers/usb/core/file.c:39 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (minor_rwsem){++++}: > down_write+0x92/0x150 kernel/locking/rwsem.c:1500 > usb_register_dev drivers/usb/core/file.c:187 [inline] > usb_register_dev+0x131/0x6a0 drivers/usb/core/file.c:156 > probe_rio.cold+0x53/0x21d drivers/usb/misc/rio500.c:468 This was caused by Oliver's commit 3864d33943b4 ("USB: rio500: refuse more than one device at a time"). It added mutex_lock(&rio500_mutex); to probe_rio(). I guess it will be necessary to add another mutex to fix this. Alan Stern
