From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + check-fops_get-return-value.patch added to -mm tree Date: Sun, 26 Oct 2008 20:40:22 -0700 Message-ID: <200810270340.m9R3eMFe030587@imap1.linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:57946 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750713AbYJ0Dkx (ORCPT ); Sun, 26 Oct 2008 23:40:53 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org Cc: laurent.pinchart@skynet.be, airlied@linux.ie, alan-jenkins@tuffmail.co.uk, mchehab@infradead.org, tiwai@suse.de, viro@zeniv.linux.org.uk The patch titled Check fops_get() return value has been added to the -mm tree. Its filename is check-fops_get-return-value.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: Check fops_get() return value From: Laurent Pinchart 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 Acked-by: Takashi Iwai Cc: Al Viro Cc: Dave Airlie Cc: Mauro Carvalho Chehab Signed-off-by: Andrew Morton --- 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(+) diff -puN drivers/gpu/drm/drm_fops.c~check-fops_get-return-value drivers/gpu/drm/drm_fops.c --- a/drivers/gpu/drm/drm_fops.c~check-fops_get-return-value +++ a/drivers/gpu/drm/drm_fops.c @@ -186,6 +186,10 @@ int drm_stub_open(struct inode *inode, s 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 -puN drivers/media/dvb/dvb-core/dvbdev.c~check-fops_get-return-value drivers/media/dvb/dvb-core/dvbdev.c --- a/drivers/media/dvb/dvb-core/dvbdev.c~check-fops_get-return-value +++ a/drivers/media/dvb/dvb-core/dvbdev.c @@ -85,6 +85,10 @@ static int dvb_device_open(struct inode 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 unlock_kernel(); return err; } +fail: unlock_kernel(); return -ENODEV; } diff -puN sound/core/sound.c~check-fops_get-return-value sound/core/sound.c --- a/sound/core/sound.c~check-fops_get-return-value +++ a/sound/core/sound.c @@ -152,6 +152,10 @@ static int __snd_open(struct inode *inod } 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) { _ Patches currently in -mm which might be from laurent.pinchart@skynet.be are check-fops_get-return-value.patch