| Message ID | Pine.LNX.4.44L0.1905201042110.1498-100000@iolanthe.rowland.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 6e41e2257f1094acc37618bf6c856115374c6922 |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | network: wireless: p54u: Fix race between disconnect and firmware loading | expand |
On Monday, May 20, 2019 4:44:21 PM CEST Alan Stern wrote: > The syzbot fuzzer found a bug in the p54 USB wireless driver. The > issue involves a race between disconnect and the firmware-loader > callback routine, and it has several aspects. > > One big problem is that when the firmware can't be loaded, the > callback routine tries to unbind the driver from the USB _device_ (by > calling device_release_driver) instead of from the USB _interface_ to > which it is actually bound (by calling usb_driver_release_interface). > > The race involves access to the private data structure. The driver's > disconnect handler waits for a completion that is signalled by the > firmware-loader callback routine. As soon as the completion is > signalled, you have to assume that the private data structure may have > been deallocated by the disconnect handler -- even if the firmware was > loaded without errors. However, the callback routine does access the > private data several times after that point. > > Another problem is that, in order to ensure that the USB device > structure hasn't been freed when the callback routine runs, the driver > takes a reference to it. This isn't good enough any more, because now > that the callback routine calls usb_driver_release_interface, it has > to ensure that the interface structure hasn't been freed. > > Finally, the driver takes an unnecessary reference to the USB device > structure in the probe function and drops the reference in the > disconnect handler. This extra reference doesn't accomplish anything, > because the USB core already guarantees that a device structure won't > be deallocated while a driver is still bound to any of its interfaces. > > To fix these problems, this patch makes the following changes: > > Call usb_driver_release_interface() rather than > device_release_driver(). > > Don't signal the completion until after the important > information has been copied out of the private data structure, > and don't refer to the private data at all thereafter. > > Lock udev (the interface's parent) before unbinding the driver > instead of locking udev->parent. > > During the firmware loading process, take a reference to the > USB interface instead of the USB device. > > Don't take an unnecessary reference to the device during probe > (and then don't drop it during disconnect). > > Signed-off-by: Alan Stern <stern@rowland.harvard.edu> > Reported-and-tested-by: syzbot+200d4bb11b23d929335f@syzkaller.appspotmail.com > CC: <stable@vger.kernel.org> Finally I'm at home where I have the device. Did some test with replugging and module unloading, all seems fine. Thanks! Acked-by: Christian Lamparter <chunkeey@gmail.com>
Alan Stern <stern@rowland.harvard.edu> writes: > The syzbot fuzzer found a bug in the p54 USB wireless driver. The > issue involves a race between disconnect and the firmware-loader > callback routine, and it has several aspects. > > One big problem is that when the firmware can't be loaded, the > callback routine tries to unbind the driver from the USB _device_ (by > calling device_release_driver) instead of from the USB _interface_ to > which it is actually bound (by calling usb_driver_release_interface). > > The race involves access to the private data structure. The driver's > disconnect handler waits for a completion that is signalled by the > firmware-loader callback routine. As soon as the completion is > signalled, you have to assume that the private data structure may have > been deallocated by the disconnect handler -- even if the firmware was > loaded without errors. However, the callback routine does access the > private data several times after that point. > > Another problem is that, in order to ensure that the USB device > structure hasn't been freed when the callback routine runs, the driver > takes a reference to it. This isn't good enough any more, because now > that the callback routine calls usb_driver_release_interface, it has > to ensure that the interface structure hasn't been freed. > > Finally, the driver takes an unnecessary reference to the USB device > structure in the probe function and drops the reference in the > disconnect handler. This extra reference doesn't accomplish anything, > because the USB core already guarantees that a device structure won't > be deallocated while a driver is still bound to any of its interfaces. > > To fix these problems, this patch makes the following changes: > > Call usb_driver_release_interface() rather than > device_release_driver(). > > Don't signal the completion until after the important > information has been copied out of the private data structure, > and don't refer to the private data at all thereafter. > > Lock udev (the interface's parent) before unbinding the driver > instead of locking udev->parent. > > During the firmware loading process, take a reference to the > USB interface instead of the USB device. > > Don't take an unnecessary reference to the device during probe > (and then don't drop it during disconnect). > > Signed-off-by: Alan Stern <stern@rowland.harvard.edu> > Reported-and-tested-by: syzbot+200d4bb11b23d929335f@syzkaller.appspotmail.com > CC: <stable@vger.kernel.org> > > --- > > > [as1899] > > > drivers/net/wireless/intersil/p54/p54usb.c | 43 ++++++++++++----------------- > 1 file changed, 18 insertions(+), 25 deletions(-) The correct prefix is "p54:", but I can fix that during commit. > Index: usb-devel/drivers/net/wireless/intersil/p54/p54usb.c > =================================================================== > --- usb-devel.orig/drivers/net/wireless/intersil/p54/p54usb.c > +++ usb-devel/drivers/net/wireless/intersil/p54/p54usb.c > @@ -33,6 +33,8 @@ MODULE_ALIAS("prism54usb"); > MODULE_FIRMWARE("isl3886usb"); > MODULE_FIRMWARE("isl3887usb"); > > +static struct usb_driver p54u_driver; How is it safe to use static variables from a wireless driver? For example, what if there are two p54 usb devices on the host? How do we avoid a race in that case?
On Tue, 28 May 2019, Kalle Valo wrote: > The correct prefix is "p54:", but I can fix that during commit. Oh, okay, thanks. > > Index: usb-devel/drivers/net/wireless/intersil/p54/p54usb.c > > =================================================================== > > --- usb-devel.orig/drivers/net/wireless/intersil/p54/p54usb.c > > +++ usb-devel/drivers/net/wireless/intersil/p54/p54usb.c > > @@ -33,6 +33,8 @@ MODULE_ALIAS("prism54usb"); > > MODULE_FIRMWARE("isl3886usb"); > > MODULE_FIRMWARE("isl3887usb"); > > > > +static struct usb_driver p54u_driver; > > How is it safe to use static variables from a wireless driver? For > example, what if there are two p54 usb devices on the host? How do we > avoid a race in that case? There is no race. This structure is not per-device; it refers only to the driver. In fact, the line above is only a forward declaration -- the actual definition of p54u_driver was already in the source file. Alan Stern
Alan Stern <stern@rowland.harvard.edu> writes: > On Tue, 28 May 2019, Kalle Valo wrote: > >> The correct prefix is "p54:", but I can fix that during commit. > > Oh, okay, thanks. > >> > Index: usb-devel/drivers/net/wireless/intersil/p54/p54usb.c >> > =================================================================== >> > --- usb-devel.orig/drivers/net/wireless/intersil/p54/p54usb.c >> > +++ usb-devel/drivers/net/wireless/intersil/p54/p54usb.c >> > @@ -33,6 +33,8 @@ MODULE_ALIAS("prism54usb"); >> > MODULE_FIRMWARE("isl3886usb"); >> > MODULE_FIRMWARE("isl3887usb"); >> > >> > +static struct usb_driver p54u_driver; >> >> How is it safe to use static variables from a wireless driver? For >> example, what if there are two p54 usb devices on the host? How do we >> avoid a race in that case? > > There is no race. This structure is not per-device; it refers only to > the driver. In fact, the line above is only a forward declaration -- > the actual definition of p54u_driver was already in the source file. Ah, I missed that. Thanks!
Alan Stern <stern@rowland.harvard.edu> wrote: > The syzbot fuzzer found a bug in the p54 USB wireless driver. The > issue involves a race between disconnect and the firmware-loader > callback routine, and it has several aspects. > > One big problem is that when the firmware can't be loaded, the > callback routine tries to unbind the driver from the USB _device_ (by > calling device_release_driver) instead of from the USB _interface_ to > which it is actually bound (by calling usb_driver_release_interface). > > The race involves access to the private data structure. The driver's > disconnect handler waits for a completion that is signalled by the > firmware-loader callback routine. As soon as the completion is > signalled, you have to assume that the private data structure may have > been deallocated by the disconnect handler -- even if the firmware was > loaded without errors. However, the callback routine does access the > private data several times after that point. > > Another problem is that, in order to ensure that the USB device > structure hasn't been freed when the callback routine runs, the driver > takes a reference to it. This isn't good enough any more, because now > that the callback routine calls usb_driver_release_interface, it has > to ensure that the interface structure hasn't been freed. > > Finally, the driver takes an unnecessary reference to the USB device > structure in the probe function and drops the reference in the > disconnect handler. This extra reference doesn't accomplish anything, > because the USB core already guarantees that a device structure won't > be deallocated while a driver is still bound to any of its interfaces. > > To fix these problems, this patch makes the following changes: > > Call usb_driver_release_interface() rather than > device_release_driver(). > > Don't signal the completion until after the important > information has been copied out of the private data structure, > and don't refer to the private data at all thereafter. > > Lock udev (the interface's parent) before unbinding the driver > instead of locking udev->parent. > > During the firmware loading process, take a reference to the > USB interface instead of the USB device. > > Don't take an unnecessary reference to the device during probe > (and then don't drop it during disconnect). > > Signed-off-by: Alan Stern <stern@rowland.harvard.edu> > Reported-and-tested-by: syzbot+200d4bb11b23d929335f@syzkaller.appspotmail.com > CC: <stable@vger.kernel.org> > Acked-by: Christian Lamparter <chunkeey@gmail.com> Patch applied to wireless-drivers-next.git, thanks. 6e41e2257f10 p54usb: Fix race between disconnect and firmware loading
Index: usb-devel/drivers/net/wireless/intersil/p54/p54usb.c =================================================================== --- usb-devel.orig/drivers/net/wireless/intersil/p54/p54usb.c +++ usb-devel/drivers/net/wireless/intersil/p54/p54usb.c @@ -33,6 +33,8 @@ MODULE_ALIAS("prism54usb"); MODULE_FIRMWARE("isl3886usb"); MODULE_FIRMWARE("isl3887usb"); +static struct usb_driver p54u_driver; + /* * Note: * @@ -921,9 +923,9 @@ static void p54u_load_firmware_cb(const { struct p54u_priv *priv = context; struct usb_device *udev = priv->udev; + struct usb_interface *intf = priv->intf; int err; - complete(&priv->fw_wait_load); if (firmware) { priv->fw = firmware; err = p54u_start_ops(priv); @@ -932,26 +934,22 @@ static void p54u_load_firmware_cb(const dev_err(&udev->dev, "Firmware not found.\n"); } - if (err) { - struct device *parent = priv->udev->dev.parent; - - dev_err(&udev->dev, "failed to initialize device (%d)\n", err); - - if (parent) - device_lock(parent); + complete(&priv->fw_wait_load); + /* + * At this point p54u_disconnect may have already freed + * the "priv" context. Do not use it anymore! + */ + priv = NULL; - device_release_driver(&udev->dev); - /* - * At this point p54u_disconnect has already freed - * the "priv" context. Do not use it anymore! - */ - priv = NULL; + if (err) { + dev_err(&intf->dev, "failed to initialize device (%d)\n", err); - if (parent) - device_unlock(parent); + usb_lock_device(udev); + usb_driver_release_interface(&p54u_driver, intf); + usb_unlock_device(udev); } - usb_put_dev(udev); + usb_put_intf(intf); } static int p54u_load_firmware(struct ieee80211_hw *dev, @@ -972,14 +970,14 @@ static int p54u_load_firmware(struct iee dev_info(&priv->udev->dev, "Loading firmware file %s\n", p54u_fwlist[i].fw); - usb_get_dev(udev); + usb_get_intf(intf); err = request_firmware_nowait(THIS_MODULE, 1, p54u_fwlist[i].fw, device, GFP_KERNEL, priv, p54u_load_firmware_cb); if (err) { dev_err(&priv->udev->dev, "(p54usb) cannot load firmware %s " "(%d)!\n", p54u_fwlist[i].fw, err); - usb_put_dev(udev); + usb_put_intf(intf); } return err; @@ -1011,8 +1009,6 @@ static int p54u_probe(struct usb_interfa skb_queue_head_init(&priv->rx_queue); init_usb_anchor(&priv->submitted); - usb_get_dev(udev); - /* really lazy and simple way of figuring out if we're a 3887 */ /* TODO: should just stick the identification in the device table */ i = intf->altsetting->desc.bNumEndpoints; @@ -1053,10 +1049,8 @@ static int p54u_probe(struct usb_interfa priv->upload_fw = p54u_upload_firmware_net2280; } err = p54u_load_firmware(dev, intf); - if (err) { - usb_put_dev(udev); + if (err) p54_free_common(dev); - } return err; } @@ -1072,7 +1066,6 @@ static void p54u_disconnect(struct usb_i wait_for_completion(&priv->fw_wait_load); p54_unregister_common(dev); - usb_put_dev(interface_to_usbdev(intf)); release_firmware(priv->fw); p54_free_common(dev); }
The syzbot fuzzer found a bug in the p54 USB wireless driver. The issue involves a race between disconnect and the firmware-loader callback routine, and it has several aspects. One big problem is that when the firmware can't be loaded, the callback routine tries to unbind the driver from the USB _device_ (by calling device_release_driver) instead of from the USB _interface_ to which it is actually bound (by calling usb_driver_release_interface). The race involves access to the private data structure. The driver's disconnect handler waits for a completion that is signalled by the firmware-loader callback routine. As soon as the completion is signalled, you have to assume that the private data structure may have been deallocated by the disconnect handler -- even if the firmware was loaded without errors. However, the callback routine does access the private data several times after that point. Another problem is that, in order to ensure that the USB device structure hasn't been freed when the callback routine runs, the driver takes a reference to it. This isn't good enough any more, because now that the callback routine calls usb_driver_release_interface, it has to ensure that the interface structure hasn't been freed. Finally, the driver takes an unnecessary reference to the USB device structure in the probe function and drops the reference in the disconnect handler. This extra reference doesn't accomplish anything, because the USB core already guarantees that a device structure won't be deallocated while a driver is still bound to any of its interfaces. To fix these problems, this patch makes the following changes: Call usb_driver_release_interface() rather than device_release_driver(). Don't signal the completion until after the important information has been copied out of the private data structure, and don't refer to the private data at all thereafter. Lock udev (the interface's parent) before unbinding the driver instead of locking udev->parent. During the firmware loading process, take a reference to the USB interface instead of the USB device. Don't take an unnecessary reference to the device during probe (and then don't drop it during disconnect). Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-and-tested-by: syzbot+200d4bb11b23d929335f@syzkaller.appspotmail.com CC: <stable@vger.kernel.org> --- [as1899] drivers/net/wireless/intersil/p54/p54usb.c | 43 ++++++++++++----------------- 1 file changed, 18 insertions(+), 25 deletions(-)