From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bruno =?UTF-8?B?UHLDqW1vbnQ=?= Date: Thu, 09 Jun 2011 06:10:19 +0000 Subject: Re: [RFC] fbmem: reset file->private_data on failed fb_open() Message-Id: <20110609081019.145ed6d5@pluto.restena.lu> List-Id: References: <20110609030628.GA10233@localhost> In-Reply-To: <20110609030628.GA10233@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Wu Fengguang Cc: "Antonino A. Daplas" , Andrew Morton , linux-fbdev@vger.kernel.org, LKML On Thu, 9 Jun 2011 11:06:28 Wu Fengguang wrote: > I wrote this when looking at NULL dereference bug > https://bugzilla.kernel.org/show_bug.cgi?id912 The trace over there rather looks like closing of a framebuffer that has been replaced (and destroyed) during boot sequence. This action happens when switching from VESA to KMS from initrd or early userspace boot sequence where plymouthd had already opened vesafb. That should hopefully be fixed by refcounting FBs as done during 2.6.39-rc7. > Will it help by clearing private_data? I have no idea at all, because > for regular files, ->release won't be called on failed ->open. Just in > case there are some exceptions in fbmem... fb devices files should be just as regular as any other device files... > --- > drivers/video/fbmem.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > --- linux-next.orig/drivers/video/fbmem.c 2011-06-09 10:36:06.000000000 +0800 > +++ linux-next/drivers/video/fbmem.c 2011-06-09 10:39:30.000000000 +0800 > @@ -1424,26 +1424,28 @@ __releases(&info->lock) > file->private_data = info; > if (info->fbops->fb_open) { > res = info->fbops->fb_open(info,1); > if (res) > module_put(info->fbops->owner); > } > #ifdef CONFIG_FB_DEFERRED_IO > if (info->fbdefio) > fb_deferred_io_open(info, inode, file); > #endif > out: > mutex_unlock(&info->lock); > - if (res) > + if (res) { > + file->private_data = NULL; > put_fb_info(info); > + } > return res; > } > > static int > fb_release(struct inode *inode, struct file *file) > __acquires(&info->lock) > __releases(&info->lock) > { > struct fb_info * const info = file->private_data; > > mutex_lock(&info->lock); > if (info->fbops->fb_release)