Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754402Ab0F1OS6 (ORCPT ); Mon, 28 Jun 2010 10:18:58 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:55703 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753828Ab0F1OS5 (ORCPT ); Mon, 28 Jun 2010 10:18:57 -0400 Date: Mon, 28 Jun 2010 10:18:56 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Andrea Righi cc: Rodolfo Giometti , Amit Walambe , Chris Leahy , Giovanni Bajo , , LKML Subject: Re: [PATCH] USB: EHCI: fix NULL pointer dererence in HCDs that use HCD_LOCAL_MEM In-Reply-To: <20100628141355.GA3807@linux.develer.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1942 Lines: 57 On Mon, 28 Jun 2010, Andrea Righi wrote: > If we use the HCD_LOCAL_MEM flag and dma_declare_coherent_memory() to > enforce the host controller's local memory utilization we also need to > disable native scatter-gather support, otherwise hcd_alloc_coherent() in > map_urb_for_dma() is called with urb->transfer_buffer == NULL, that > triggers a NULL pointer dereference. > > We can also consider to add a WARN_ON() and return an error code to > better catch this problem in the future. > > Signed-off-by: Andrea Righi > --- > drivers/usb/core/hcd.c | 5 +++++ > drivers/usb/host/ehci-hcd.c | 3 ++- > 2 files changed, 7 insertions(+), 1 deletions(-) > > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c > index 12742f1..161c757 100644 > --- a/drivers/usb/core/hcd.c > +++ b/drivers/usb/core/hcd.c > @@ -1219,6 +1219,11 @@ static int hcd_alloc_coherent(struct usb_bus *bus, > { > unsigned char *vaddr; > > + if (*vaddr_handle == NULL) { > + WARN_ON_ONCE(1); > + return -EFAULT; > + } > + > vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr), > mem_flags, dma_handle); > if (!vaddr) > diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c > index a3ef2a9..27e0351 100644 > --- a/drivers/usb/host/ehci-hcd.c > +++ b/drivers/usb/host/ehci-hcd.c > @@ -606,7 +606,8 @@ static int ehci_init(struct usb_hcd *hcd) > ehci->command = temp; > > /* Accept arbitrarily long scatter-gather lists */ > - hcd->self.sg_tablesize = ~0; > + if (!(hcd->driver->flags & HCD_LOCAL_MEM)) > + hcd->self.sg_tablesize = ~0; > return 0; > } Looks okay to me. You can add my Acked-by: when you submit this to Greg KH. Alan Stern -- 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/