Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756440AbZLOEpw (ORCPT ); Mon, 14 Dec 2009 23:45:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756299AbZLOEpv (ORCPT ); Mon, 14 Dec 2009 23:45:51 -0500 Received: from mail-gx0-f211.google.com ([209.85.217.211]:59925 "EHLO mail-gx0-f211.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755252AbZLOEpu (ORCPT ); Mon, 14 Dec 2009 23:45:50 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer; b=mYjdjlweYSoUPNK6TCiL6smfJtdhPSAFzyqH5Ye2pXAdb3xB+UR+y45xZb5/fazVy2 7+8mw93GgIVSlei00VlrOe4wCx3/IHNdgBBOwwobAltHWwGIELaHAonPjALPCWDg/iJZ z7F0r4y9JMBwPoTeLBzUk/09kiMp/gJpFcf40= Subject: Re: [GIT PATCH] USB patches for 2.6.33-git From: Russ Dill To: Linus Torvalds Cc: Greg KH , Alan Stern , Greg KH , Andrew Morton , Linux Kernel Mailing List , linux-usb@vger.kernel.org In-Reply-To: References: <1260849652.28808.1.camel@russ-laptop> Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-vtpnKbHsLFrNLKj7DtFL" Date: Mon, 14 Dec 2009 21:45:35 -0700 Message-ID: <1260852335.1886.0.camel@russ-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5527 Lines: 170 --=-vtpnKbHsLFrNLKj7DtFL Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2009-12-14 at 20:36 -0800, Linus Torvalds wrote: >=20 > On Mon, 14 Dec 2009, Russ Dill wrote: > > @@ -144,10 +144,9 @@ static int __find_interface(struct device *dev, vo= id *data) > > return 0; > > =20 > > intf =3D to_usb_interface(dev); > > - if (intf->minor !=3D -1 && intf->minor =3D=3D arg->minor) { > > - arg->interface =3D intf; > > + if (intf->minor !=3D -1 && intf->minor =3D=3D arg->minor && > > + dev->driver =3D=3D arg->drv) > > return 1; > > - } > > return 0; > > } >=20 > Btw, can we please write this somewhat more readably, and just do >=20 > if (dev->driver !=3D arg->drv) > return 0; > intf =3D to_usb_interface(dev); > return intf->minor =3D=3D arg->minor; >=20 > because the whole "intf->minor !=3D -1" thing is pointless (we're going t= o=20 > test it against 'arg->minor', and if that is -1, then the caller damn wel= l=20 > gets what he deserves anyway). >=20 > This way there are no complex multi-line crud expressions, and it all=20 > looks simpler. No? Yup. =46rom 41e394bc38b9d5224cc5e8013f45e769910a114e Mon Sep 17 00:00:00 2001 From: Russ Dill Date: Wed, 18 Nov 2009 10:31:27 -0700 Subject: [PATCH] Close usb_find_interface race v3 USB drivers that create character devices call usb_register_dev in their probe function. This associates the usb_interface device with that minor number and creates the character device and announces it to the world. However, the driver's probe function is called before the new usb_interface is added to the driver's klist_devices. This is a problem because userspace will respond to the character device creation announcement by opening the character device. The driver's open function will the call usb_find_interface to find the usb_interface associated with that minor number. usb_find_interface will walk the driver's list of devices and find the usb_interface with the matching minor number. Because the announcement happens before the usb_interface is added to the driver's klist_devices, a race condition exists. A straightforward fix is to walk the list of devices on usb_bus_type instead since the device is added to that list before the announcement occurs. bus_find_device calls get_device to bump the reference count on the found device. It is arguable that the reference count should be dropped by the caller of usb_find_interface instead of usb_find_interface, however, the current users of usb_find_interface do not expect this. The original version of this patch only matched against minor number instead of driver and minor number. This version matches against both. Signed-off-by: Russ Dill --- drivers/usb/core/usb.c | 31 ++++++++++++++++--------------- 1 files changed, 16 insertions(+), 15 deletions(-) diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c index b1b85ab..52e5e31 100644 --- a/drivers/usb/core/usb.c +++ b/drivers/usb/core/usb.c @@ -132,7 +132,7 @@ EXPORT_SYMBOL_GPL(usb_altnum_to_altsetting); =20 struct find_interface_arg { int minor; - struct usb_interface *interface; + struct device_driver *drv; }; =20 static int __find_interface(struct device *dev, void *data) @@ -143,12 +143,10 @@ static int __find_interface(struct device *dev, void = *data) if (!is_usb_interface(dev)) return 0; =20 + if (dev->driver !=3D arg->drv) + return 0; intf =3D to_usb_interface(dev); - if (intf->minor !=3D -1 && intf->minor =3D=3D arg->minor) { - arg->interface =3D intf; - return 1; - } - return 0; + return intf->minor =3D=3D arg->minor; } =20 /** @@ -156,21 +154,24 @@ static int __find_interface(struct device *dev, void = *data) * @drv: the driver whose current configuration is considered * @minor: the minor number of the desired device * - * This walks the driver device list and returns a pointer to the interfac= e - * with the matching minor. Note, this only works for devices that share = the - * USB major number. + * This walks the bus device list and returns a pointer to the interface + * with the matching minor and driver. Note, this only works for devices + * that share the USB major number. */ struct usb_interface *usb_find_interface(struct usb_driver *drv, int minor= ) { struct find_interface_arg argb; - int retval; + struct device *dev; =20 argb.minor =3D minor; - argb.interface =3D NULL; - /* eat the error, it will be in argb.interface */ - retval =3D driver_for_each_device(&drv->drvwrap.driver, NULL, &argb, - __find_interface); - return argb.interface; + argb.drv =3D &drv->drvwrap.driver; + + dev =3D bus_find_device(&usb_bus_type, NULL, &argb, __find_interface); + + /* Drop reference count from bus_find_device */ + put_device(dev); + + return dev ? to_usb_interface(dev) : NULL; } EXPORT_SYMBOL_GPL(usb_find_interface); =20 --=20 1.6.5 --=-vtpnKbHsLFrNLKj7DtFL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEABECAAYFAksnFGkACgkQfNRrxBinbdv9vQCgmLGSWoROcE5sAUNuxjb41S9f LzYAn26/tc97Lcjj6S+Amjga72IxgBq0 =+s8d -----END PGP SIGNATURE----- --=-vtpnKbHsLFrNLKj7DtFL-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/