From 9472aff16ca0fd9351eea7773facef364743088f Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Thu, 8 Aug 2019 13:34:08 -0400 Subject: [PATCH] USB: rio500: Fix lockdep violation The syzbot fuzzer found a lockdep violation in the rio500 driver: ====================================================== 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 problem is that the driver's open_rio() routine is called while the usbcore's minor_rwsem is locked for reading, and it acquires the rio500_mutex; whereas conversely, probe_rio() and disconnect_rio() first acquire the rio500_mutex and then call usb_register_dev() or usb_deregister_dev(), which lock minor_rwsem for writing. The correct ordering of acquisition should be: minor_rwsem first, then rio500_mutex (since the locking in open_rio() cannot be changed). Thus, the probe and disconnect routines should avoid holding rio500_mutex while doing their registration and deregistration. This patch adjusts the code in those two routines to do just that. It also relies on the fact that the probe and disconnect routines are protected by the device mutex, so the initial test of rio->present needs no extra locking. Reported-by: syzbot+7bbcbe9c9ff0cd49592a@syzkaller.appspotmail.com Signed-off-by: Alan Stern Fixes: d710734b0677 ("USB: rio500: simplify locking") Acked-by: Oliver Neukum CC: Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1908081329240.1319-100000@iolanthe.rowland.org Signed-off-by: Greg Kroah-Hartman --- drivers/usb/misc/rio500.c | 72 +++++++++++++++++++++------------------ 1 file changed, 38 insertions(+), 34 deletions(-) diff --git a/drivers/usb/misc/rio500.c b/drivers/usb/misc/rio500.c index 27e9c78a791e..30cae5e1954d 100644 --- a/drivers/usb/misc/rio500.c +++ b/drivers/usb/misc/rio500.c @@ -454,51 +454,55 @@ static int probe_rio(struct usb_interface *intf, { struct usb_device *dev = interface_to_usbdev(intf); struct rio_usb_data *rio = &rio_instance; - int retval = 0; + int retval = -ENOMEM; + char *ibuf, *obuf; - mutex_lock(&rio500_mutex); if (rio->present) { dev_info(&intf->dev, "Second USB Rio at address %d refused\n", dev->devnum); - retval = -EBUSY; - goto bail_out; - } else { - dev_info(&intf->dev, "USB Rio found at address %d\n", dev->devnum); + return -EBUSY; } + dev_info(&intf->dev, "USB Rio found at address %d\n", dev->devnum); + + obuf = kmalloc(OBUF_SIZE, GFP_KERNEL); + if (!obuf) { + dev_err(&dev->dev, + "probe_rio: Not enough memory for the output buffer\n"); + goto err_obuf; + } + dev_dbg(&intf->dev, "obuf address: %p\n", obuf); + + ibuf = kmalloc(IBUF_SIZE, GFP_KERNEL); + if (!ibuf) { + dev_err(&dev->dev, + "probe_rio: Not enough memory for the input buffer\n"); + goto err_ibuf; + } + dev_dbg(&intf->dev, "ibuf address: %p\n", ibuf); + + mutex_lock(&rio500_mutex); + rio->rio_dev = dev; + rio->ibuf = ibuf; + rio->obuf = obuf; + rio->present = 1; + mutex_unlock(&rio500_mutex); retval = usb_register_dev(intf, &usb_rio_class); if (retval) { dev_err(&dev->dev, "Not able to get a minor for this device.\n"); - retval = -ENOMEM; - goto bail_out; + goto err_register; } - rio->rio_dev = dev; + usb_set_intfdata(intf, rio); + return retval; - if (!(rio->obuf = kmalloc(OBUF_SIZE, GFP_KERNEL))) { - dev_err(&dev->dev, - "probe_rio: Not enough memory for the output buffer\n"); - usb_deregister_dev(intf, &usb_rio_class); - retval = -ENOMEM; - goto bail_out; - } - dev_dbg(&intf->dev, "obuf address:%p\n", rio->obuf); - - if (!(rio->ibuf = kmalloc(IBUF_SIZE, GFP_KERNEL))) { - dev_err(&dev->dev, - "probe_rio: Not enough memory for the input buffer\n"); - usb_deregister_dev(intf, &usb_rio_class); - kfree(rio->obuf); - retval = -ENOMEM; - goto bail_out; - } - dev_dbg(&intf->dev, "ibuf address:%p\n", rio->ibuf); - - usb_set_intfdata (intf, rio); - rio->present = 1; -bail_out: + err_register: + mutex_lock(&rio500_mutex); + rio->present = 0; mutex_unlock(&rio500_mutex); - + err_ibuf: + kfree(obuf); + err_obuf: return retval; } @@ -507,10 +511,10 @@ static void disconnect_rio(struct usb_interface *intf) struct rio_usb_data *rio = usb_get_intfdata (intf); usb_set_intfdata (intf, NULL); - mutex_lock(&rio500_mutex); if (rio) { usb_deregister_dev(intf, &usb_rio_class); + mutex_lock(&rio500_mutex); if (rio->isopen) { rio->isopen = 0; /* better let it finish - the release will do whats needed */ @@ -524,8 +528,8 @@ static void disconnect_rio(struct usb_interface *intf) dev_info(&intf->dev, "USB Rio disconnected.\n"); rio->present = 0; + mutex_unlock(&rio500_mutex); } - mutex_unlock(&rio500_mutex); } static const struct usb_device_id rio_table[] = {