From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valentine Barshak Subject: Re: [PATCH 1/2] USB: HID: Fix race between disconnect and hiddev_ioctl Date: Tue, 07 Dec 2010 18:02:46 +0300 Message-ID: <4CFE4C96.4000702@mvista.com> References: <20101206145141.GA8462@mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Jiri Kosina Cc: linux-usb@vger.kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-input@vger.kernel.org Jiri Kosina wrote: > On Mon, 6 Dec 2010, Valentine Barshak wrote: > > >> A USB HID device can be disconnected at any time. >> If this happens right before or while hiddev_ioctl is in progress, >> the hiddev_ioctl tries to access invalid hiddev->hid pointer. >> When the hid device is disconnected, the hiddev_disconnect() >> ends up with a call to hid_device_release() which frees >> hid_device, but doesn't set the hiddev->hid pointer to NULL. >> If the deallocated memory region has been re-used by the kernel, >> this can cause a crash or memory corruption. >> >> Since disconnect can happen at any time, we can't initialize >> struct hid_device *hid = hiddev->hid at the beginning of ioctl >> and then use it. >> >> This change checks hiddev->exist flag while holding >> the existancelock and uses hid_device only if it exists. >> > > The code duplication isn't really particularly nice, but I don't see any > way around it that wouldn't complicate things even more. > > I will be applying the patches, thanks. > Thanks! > (BTW your patches didn't reach mail mailbox, I had to dig them out from > mailinglist -- did you receive bounces by any chance?). > Yes, they did bounce. Thanks, Val. > Thanks, > >