Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755295AbYJPNCq (ORCPT ); Thu, 16 Oct 2008 09:02:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752293AbYJPNCi (ORCPT ); Thu, 16 Oct 2008 09:02:38 -0400 Received: from mailrelay005.isp.belgacom.be ([195.238.6.171]:36540 "EHLO mailrelay005.isp.belgacom.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751534AbYJPNCi (ORCPT ); Thu, 16 Oct 2008 09:02:38 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ApsEANvY9kjCTsYx/2dsb2JhbACBcsFkg2w From: Laurent Pinchart To: linux-kernel@vger.kernel.org Subject: [PATCH] Check fops_get() return value Date: Thu, 16 Oct 2008 15:02:40 +0200 User-Agent: KMail/1.9.9 X-Face: 4Mf^tnii7k\_EnR5aobBm6Di[DZ9@AX1wJ"okBdX-UoJ>:SRn]c6DDU"qUIwfs98vF>Tnf SacR{(0Du"N%_.#X]"TXx)A'gKB1i7SK$CTLuy{h})c=g:'w3 Cc: airlied@linux.ie, mchehab@infradead.org, perex@perex.cz, tiwai@suse.de, alan-jenkins@tuffmail.co.uk MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200810161502.41159.laurent.pinchart@skynet.be> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2768 Lines: 80 Several subsystem open handlers dereference the fops_get() return value without checking it for nullness. This opens a race condition between the open handler and module unloading. A module can be marked as being unloaded (MODULE_STATE_GOING) before its exit function is called and gets the chance to unregister the driver. During that window open handlers can still be called, and fops_get() will fail in try_module_get() and return a NULL pointer. This change checks the fops_get() return value and returns -ENODEV if NULL. Reported-by: Alan Jenkins Signed-off-by: Laurent Pinchart --- drivers/gpu/drm/drm_fops.c | 4 ++++ drivers/media/dvb/dvb-core/dvbdev.c | 5 +++++ sound/core/sound.c | 4 ++++ 3 files changed, 13 insertions(+), 0 deletions(-) diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c index 851a53f..ef5c295 100644 --- a/drivers/gpu/drm/drm_fops.c +++ b/drivers/gpu/drm/drm_fops.c @@ -186,6 +186,10 @@ int drm_stub_open(struct inode *inode, struct file *filp) old_fops = filp->f_op; filp->f_op = fops_get(&dev->driver->fops); + if (filp->f_op == NULL) { + filp->f_op = old_fops; + goto out; + } if (filp->f_op->open && (err = filp->f_op->open(inode, filp))) { fops_put(filp->f_op); filp->f_op = fops_get(old_fops); diff --git a/drivers/media/dvb/dvb-core/dvbdev.c b/drivers/media/dvb/dvb-core/dvbdev.c index e713277..fb4e241 100644 --- a/drivers/media/dvb/dvb-core/dvbdev.c +++ b/drivers/media/dvb/dvb-core/dvbdev.c @@ -85,6 +85,10 @@ static int dvb_device_open(struct inode *inode, struct file *file) file->private_data = dvbdev; old_fops = file->f_op; file->f_op = fops_get(dvbdev->fops); + if (file->f_op == NULL) { + file->f_op = old_fops; + goto fail; + } if(file->f_op->open) err = file->f_op->open(inode,file); if (err) { @@ -95,6 +99,7 @@ static int dvb_device_open(struct inode *inode, struct file *file) unlock_kernel(); return err; } +fail: unlock_kernel(); return -ENODEV; } diff --git a/sound/core/sound.c b/sound/core/sound.c index c0685e2..8659b84 100644 --- a/sound/core/sound.c +++ b/sound/core/sound.c @@ -152,6 +152,10 @@ static int __snd_open(struct inode *inode, struct file *file) } old_fops = file->f_op; file->f_op = fops_get(mptr->f_ops); + if (file->f_op == NULL) { + file->f_op = old_fops; + return -ENODEV; + } if (file->f_op->open) err = file->f_op->open(inode, file); if (err) { -- 1.5.0 -- 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/