[PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[Takashi Iwai]

When a fbdev with deferred I/O is once opened and closed, the dirty
pages still remain queued in the pageref list, and eventually later
those may be processed in the delayed work.  This may lead to a
corruption of pages, hitting an Oops.

This patch makes sure to cancel the delayed work and clean up the
pageref list at closing the device for addressing the bug.  A part of
the cleanup code is factored out as a new helper function that is
called from the common fb_release().

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 drivers/video/fbdev/core/fb_defio.c | 10 +++++++++-
 drivers/video/fbdev/core/fbmem.c    |  2 ++
 include/linux/fb.h                  |  1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index c730253ab85c..583cbcf09446 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -313,7 +313,7 @@ void fb_deferred_io_open(struct fb_info *info,
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_open);
 
-void fb_deferred_io_cleanup(struct fb_info *info)
+void fb_deferred_io_release(struct fb_info *info)
 {
 	struct fb_deferred_io *fbdefio = info->fbdefio;
 	struct page *page;
@@ -327,6 +327,14 @@ void fb_deferred_io_cleanup(struct fb_info *info)
 		page = fb_deferred_io_page(info, i);
 		page->mapping = NULL;
 	}
+}
+EXPORT_SYMBOL_GPL(fb_deferred_io_release);
+
+void fb_deferred_io_cleanup(struct fb_info *info)
+{
+	struct fb_deferred_io *fbdefio = info->fbdefio;
+
+	fb_deferred_io_release(info);
 
 	kvfree(info->pagerefs);
 	mutex_destroy(&fbdefio->lock);
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 3a6c8458eb8d..78c4cb5ee7c9 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1454,6 +1454,8 @@ __releases(&info->lock)
 	struct fb_info * const info = file->private_data;
 
 	lock_fb_info(info);
+	if (info->fbdefio)
+		fb_deferred_io_release(info);
 	if (info->fbops->fb_release)
 		info->fbops->fb_release(info,1);
 	module_put(info->fbops->owner);
diff --git a/include/linux/fb.h b/include/linux/fb.h
index 96b96323e9cb..73eb1f85ea8e 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -662,6 +662,7 @@ extern int  fb_deferred_io_init(struct fb_info *info);
 extern void fb_deferred_io_open(struct fb_info *info,
 				struct inode *inode,
 				struct file *file);
+extern void fb_deferred_io_release(struct fb_info *info);
 extern void fb_deferred_io_cleanup(struct fb_info *info);
 extern int fb_deferred_io_fsync(struct file *file, loff_t start,
 				loff_t end, int datasync);
-- 
2.35.3

[PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[Takashi Iwai]

When a fbdev with deferred I/O is once opened and closed, the dirty
pages still remain queued in the pageref list, and eventually later
those may be processed in the delayed work.  This may lead to a
corruption of pages, hitting an Oops.

This patch makes sure to cancel the delayed work and clean up the
pageref list at closing the device for addressing the bug.  A part of
the cleanup code is factored out as a new helper function that is
called from the common fb_release().

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 drivers/video/fbdev/core/fb_defio.c | 10 +++++++++-
 drivers/video/fbdev/core/fbmem.c    |  2 ++
 include/linux/fb.h                  |  1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index c730253ab85c..583cbcf09446 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -313,7 +313,7 @@ void fb_deferred_io_open(struct fb_info *info,
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_open);
 
-void fb_deferred_io_cleanup(struct fb_info *info)
+void fb_deferred_io_release(struct fb_info *info)
 {
 	struct fb_deferred_io *fbdefio = info->fbdefio;
 	struct page *page;
@@ -327,6 +327,14 @@ void fb_deferred_io_cleanup(struct fb_info *info)
 		page = fb_deferred_io_page(info, i);
 		page->mapping = NULL;
 	}
+}
+EXPORT_SYMBOL_GPL(fb_deferred_io_release);
+
+void fb_deferred_io_cleanup(struct fb_info *info)
+{
+	struct fb_deferred_io *fbdefio = info->fbdefio;
+
+	fb_deferred_io_release(info);
 
 	kvfree(info->pagerefs);
 	mutex_destroy(&fbdefio->lock);
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 3a6c8458eb8d..78c4cb5ee7c9 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1454,6 +1454,8 @@ __releases(&info->lock)
 	struct fb_info * const info = file->private_data;
 
 	lock_fb_info(info);
+	if (info->fbdefio)
+		fb_deferred_io_release(info);
 	if (info->fbops->fb_release)
 		info->fbops->fb_release(info,1);
 	module_put(info->fbops->owner);
diff --git a/include/linux/fb.h b/include/linux/fb.h
index 96b96323e9cb..73eb1f85ea8e 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -662,6 +662,7 @@ extern int  fb_deferred_io_init(struct fb_info *info);
 extern void fb_deferred_io_open(struct fb_info *info,
 				struct inode *inode,
 				struct file *file);
+extern void fb_deferred_io_release(struct fb_info *info);
 extern void fb_deferred_io_cleanup(struct fb_info *info);
 extern int fb_deferred_io_fsync(struct file *file, loff_t start,
 				loff_t end, int datasync);
-- 
2.35.3

Re: [PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[Patrik Jakobsson]

On Fri, Jan 27, 2023 at 05:58:34PM +0100, Takashi Iwai wrote:
> When a fbdev with deferred I/O is once opened and closed, the dirty
> pages still remain queued in the pageref list, and eventually later
> those may be processed in the delayed work.  This may lead to a
> corruption of pages, hitting an Oops.
> 
> This patch makes sure to cancel the delayed work and clean up the
> pageref list at closing the device for addressing the bug.  A part of
> the cleanup code is factored out as a new helper function that is
> called from the common fb_release().
> 
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

Reviewed-by: Patrik Jakobsson <pjakobsson@suse.de>

> ---
>  drivers/video/fbdev/core/fb_defio.c | 10 +++++++++-
>  drivers/video/fbdev/core/fbmem.c    |  2 ++
>  include/linux/fb.h                  |  1 +
>  3 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
> index c730253ab85c..583cbcf09446 100644
> --- a/drivers/video/fbdev/core/fb_defio.c
> +++ b/drivers/video/fbdev/core/fb_defio.c
> @@ -313,7 +313,7 @@ void fb_deferred_io_open(struct fb_info *info,
>  }
>  EXPORT_SYMBOL_GPL(fb_deferred_io_open);
>  
> -void fb_deferred_io_cleanup(struct fb_info *info)
> +void fb_deferred_io_release(struct fb_info *info)
>  {
>  	struct fb_deferred_io *fbdefio = info->fbdefio;
>  	struct page *page;
> @@ -327,6 +327,14 @@ void fb_deferred_io_cleanup(struct fb_info *info)
>  		page = fb_deferred_io_page(info, i);
>  		page->mapping = NULL;
>  	}
> +}
> +EXPORT_SYMBOL_GPL(fb_deferred_io_release);
> +
> +void fb_deferred_io_cleanup(struct fb_info *info)
> +{
> +	struct fb_deferred_io *fbdefio = info->fbdefio;
> +
> +	fb_deferred_io_release(info);
>  
>  	kvfree(info->pagerefs);
>  	mutex_destroy(&fbdefio->lock);
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 3a6c8458eb8d..78c4cb5ee7c9 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1454,6 +1454,8 @@ __releases(&info->lock)
>  	struct fb_info * const info = file->private_data;
>  
>  	lock_fb_info(info);
> +	if (info->fbdefio)
> +		fb_deferred_io_release(info);
>  	if (info->fbops->fb_release)
>  		info->fbops->fb_release(info,1);
>  	module_put(info->fbops->owner);
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 96b96323e9cb..73eb1f85ea8e 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -662,6 +662,7 @@ extern int  fb_deferred_io_init(struct fb_info *info);
>  extern void fb_deferred_io_open(struct fb_info *info,
>  				struct inode *inode,
>  				struct file *file);
> +extern void fb_deferred_io_release(struct fb_info *info);
>  extern void fb_deferred_io_cleanup(struct fb_info *info);
>  extern int fb_deferred_io_fsync(struct file *file, loff_t start,
>  				loff_t end, int datasync);
> -- 
> 2.35.3
> 

Re: [PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[Patrik Jakobsson]

On Fri, Jan 27, 2023 at 05:58:34PM +0100, Takashi Iwai wrote:
> When a fbdev with deferred I/O is once opened and closed, the dirty
> pages still remain queued in the pageref list, and eventually later
> those may be processed in the delayed work.  This may lead to a
> corruption of pages, hitting an Oops.
> 
> This patch makes sure to cancel the delayed work and clean up the
> pageref list at closing the device for addressing the bug.  A part of
> the cleanup code is factored out as a new helper function that is
> called from the common fb_release().
> 
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

Reviewed-by: Patrik Jakobsson <pjakobsson@suse.de>

> ---
>  drivers/video/fbdev/core/fb_defio.c | 10 +++++++++-
>  drivers/video/fbdev/core/fbmem.c    |  2 ++
>  include/linux/fb.h                  |  1 +
>  3 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
> index c730253ab85c..583cbcf09446 100644
> --- a/drivers/video/fbdev/core/fb_defio.c
> +++ b/drivers/video/fbdev/core/fb_defio.c
> @@ -313,7 +313,7 @@ void fb_deferred_io_open(struct fb_info *info,
>  }
>  EXPORT_SYMBOL_GPL(fb_deferred_io_open);
>  
> -void fb_deferred_io_cleanup(struct fb_info *info)
> +void fb_deferred_io_release(struct fb_info *info)
>  {
>  	struct fb_deferred_io *fbdefio = info->fbdefio;
>  	struct page *page;
> @@ -327,6 +327,14 @@ void fb_deferred_io_cleanup(struct fb_info *info)
>  		page = fb_deferred_io_page(info, i);
>  		page->mapping = NULL;
>  	}
> +}
> +EXPORT_SYMBOL_GPL(fb_deferred_io_release);
> +
> +void fb_deferred_io_cleanup(struct fb_info *info)
> +{
> +	struct fb_deferred_io *fbdefio = info->fbdefio;
> +
> +	fb_deferred_io_release(info);
>  
>  	kvfree(info->pagerefs);
>  	mutex_destroy(&fbdefio->lock);
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 3a6c8458eb8d..78c4cb5ee7c9 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1454,6 +1454,8 @@ __releases(&info->lock)
>  	struct fb_info * const info = file->private_data;
>  
>  	lock_fb_info(info);
> +	if (info->fbdefio)
> +		fb_deferred_io_release(info);
>  	if (info->fbops->fb_release)
>  		info->fbops->fb_release(info,1);
>  	module_put(info->fbops->owner);
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 96b96323e9cb..73eb1f85ea8e 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -662,6 +662,7 @@ extern int  fb_deferred_io_init(struct fb_info *info);
>  extern void fb_deferred_io_open(struct fb_info *info,
>  				struct inode *inode,
>  				struct file *file);
> +extern void fb_deferred_io_release(struct fb_info *info);
>  extern void fb_deferred_io_cleanup(struct fb_info *info);
>  extern int fb_deferred_io_fsync(struct file *file, loff_t start,
>  				loff_t end, int datasync);
> -- 
> 2.35.3
> 

Re: [PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[kernel test robot]

Hi Takashi,

I love your patch! Yet something to improve:

[auto build test ERROR on drm-misc/drm-misc-next]
[also build test ERROR on linus/master v6.2-rc5 next-20230127]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Takashi-Iwai/fbdev-Fix-invalid-page-access-after-closing-deferred-I-O-devices/20230128-180330
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20230127165834.11387-1-tiwai%40suse.de
patch subject: [PATCH] fbdev: Fix invalid page access after closing deferred I/O devices
config: s390-defconfig (https://download.01.org/0day-ci/archive/20230129/202301290917.puRyNsug-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/f28e22b16f34068d07913fa5d4fb2c9683aa8dc4
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Takashi-Iwai/fbdev-Fix-invalid-page-access-after-closing-deferred-I-O-devices/20230128-180330
        git checkout f28e22b16f34068d07913fa5d4fb2c9683aa8dc4
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/video/fbdev/core/fbmem.c: In function 'fb_release':
>> drivers/video/fbdev/core/fbmem.c:1456:17: error: 'struct fb_info' has no member named 'fbdefio'
    1456 |         if (info->fbdefio)
         |                 ^~


vim +1456 drivers/video/fbdev/core/fbmem.c

  1447	
  1448	static int
  1449	fb_release(struct inode *inode, struct file *file)
  1450	__acquires(&info->lock)
  1451	__releases(&info->lock)
  1452	{
  1453		struct fb_info * const info = file->private_data;
  1454	
  1455		lock_fb_info(info);
> 1456		if (info->fbdefio)
  1457			fb_deferred_io_release(info);
  1458		if (info->fbops->fb_release)
  1459			info->fbops->fb_release(info,1);
  1460		module_put(info->fbops->owner);
  1461		unlock_fb_info(info);
  1462		put_fb_info(info);
  1463		return 0;
  1464	}
  1465	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[kernel test robot]

Hi Takashi,

I love your patch! Yet something to improve:

[auto build test ERROR on drm-misc/drm-misc-next]
[also build test ERROR on linus/master v6.2-rc5 next-20230127]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Takashi-Iwai/fbdev-Fix-invalid-page-access-after-closing-deferred-I-O-devices/20230128-180330
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20230127165834.11387-1-tiwai%40suse.de
patch subject: [PATCH] fbdev: Fix invalid page access after closing deferred I/O devices
config: s390-defconfig (https://download.01.org/0day-ci/archive/20230129/202301290917.puRyNsug-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/f28e22b16f34068d07913fa5d4fb2c9683aa8dc4
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Takashi-Iwai/fbdev-Fix-invalid-page-access-after-closing-deferred-I-O-devices/20230128-180330
        git checkout f28e22b16f34068d07913fa5d4fb2c9683aa8dc4
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/video/fbdev/core/fbmem.c: In function 'fb_release':
>> drivers/video/fbdev/core/fbmem.c:1456:17: error: 'struct fb_info' has no member named 'fbdefio'
    1456 |         if (info->fbdefio)
         |                 ^~


vim +1456 drivers/video/fbdev/core/fbmem.c

  1447	
  1448	static int
  1449	fb_release(struct inode *inode, struct file *file)
  1450	__acquires(&info->lock)
  1451	__releases(&info->lock)
  1452	{
  1453		struct fb_info * const info = file->private_data;
  1454	
  1455		lock_fb_info(info);
> 1456		if (info->fbdefio)
  1457			fb_deferred_io_release(info);
  1458		if (info->fbops->fb_release)
  1459			info->fbops->fb_release(info,1);
  1460		module_put(info->fbops->owner);
  1461		unlock_fb_info(info);
  1462		put_fb_info(info);
  1463		return 0;
  1464	}
  1465	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[Patrik Jakobsson]

On Fri, Jan 27, 2023 at 5:58 PM Takashi Iwai <tiwai@suse.de> wrote:
>
> When a fbdev with deferred I/O is once opened and closed, the dirty
> pages still remain queued in the pageref list, and eventually later
> those may be processed in the delayed work.  This may lead to a
> corruption of pages, hitting an Oops.
>
> This patch makes sure to cancel the delayed work and clean up the
> pageref list at closing the device for addressing the bug.  A part of
> the cleanup code is factored out as a new helper function that is
> called from the common fb_release().
>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

For some reason my first review didn't make it to the list. Trying
again with my other email.

As kernel test robot says, we need to check CONFIG_FB_DEFERRED_IO
around access to info->fbdefio.

With that fixed:
Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>

> ---
>  drivers/video/fbdev/core/fb_defio.c | 10 +++++++++-
>  drivers/video/fbdev/core/fbmem.c    |  2 ++
>  include/linux/fb.h                  |  1 +
>  3 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
> index c730253ab85c..583cbcf09446 100644
> --- a/drivers/video/fbdev/core/fb_defio.c
> +++ b/drivers/video/fbdev/core/fb_defio.c
> @@ -313,7 +313,7 @@ void fb_deferred_io_open(struct fb_info *info,
>  }
>  EXPORT_SYMBOL_GPL(fb_deferred_io_open);
>
> -void fb_deferred_io_cleanup(struct fb_info *info)
> +void fb_deferred_io_release(struct fb_info *info)
>  {
>         struct fb_deferred_io *fbdefio = info->fbdefio;
>         struct page *page;
> @@ -327,6 +327,14 @@ void fb_deferred_io_cleanup(struct fb_info *info)
>                 page = fb_deferred_io_page(info, i);
>                 page->mapping = NULL;
>         }
> +}
> +EXPORT_SYMBOL_GPL(fb_deferred_io_release);
> +
> +void fb_deferred_io_cleanup(struct fb_info *info)
> +{
> +       struct fb_deferred_io *fbdefio = info->fbdefio;
> +
> +       fb_deferred_io_release(info);
>
>         kvfree(info->pagerefs);
>         mutex_destroy(&fbdefio->lock);
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 3a6c8458eb8d..78c4cb5ee7c9 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1454,6 +1454,8 @@ __releases(&info->lock)
>         struct fb_info * const info = file->private_data;
>
>         lock_fb_info(info);
> +       if (info->fbdefio)
> +               fb_deferred_io_release(info);
>         if (info->fbops->fb_release)
>                 info->fbops->fb_release(info,1);
>         module_put(info->fbops->owner);
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 96b96323e9cb..73eb1f85ea8e 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -662,6 +662,7 @@ extern int  fb_deferred_io_init(struct fb_info *info);
>  extern void fb_deferred_io_open(struct fb_info *info,
>                                 struct inode *inode,
>                                 struct file *file);
> +extern void fb_deferred_io_release(struct fb_info *info);
>  extern void fb_deferred_io_cleanup(struct fb_info *info);
>  extern int fb_deferred_io_fsync(struct file *file, loff_t start,
>                                 loff_t end, int datasync);
> --
> 2.35.3
>

Re: [PATCH] fbdev: Fix invalid page access after closing deferred I/O devices

[Patrik Jakobsson]

On Fri, Jan 27, 2023 at 5:58 PM Takashi Iwai <tiwai@suse.de> wrote:
>
> When a fbdev with deferred I/O is once opened and closed, the dirty
> pages still remain queued in the pageref list, and eventually later
> those may be processed in the delayed work.  This may lead to a
> corruption of pages, hitting an Oops.
>
> This patch makes sure to cancel the delayed work and clean up the
> pageref list at closing the device for addressing the bug.  A part of
> the cleanup code is factored out as a new helper function that is
> called from the common fb_release().
>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

For some reason my first review didn't make it to the list. Trying
again with my other email.

As kernel test robot says, we need to check CONFIG_FB_DEFERRED_IO
around access to info->fbdefio.

With that fixed:
Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>

> ---
>  drivers/video/fbdev/core/fb_defio.c | 10 +++++++++-
>  drivers/video/fbdev/core/fbmem.c    |  2 ++
>  include/linux/fb.h                  |  1 +
>  3 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
> index c730253ab85c..583cbcf09446 100644
> --- a/drivers/video/fbdev/core/fb_defio.c
> +++ b/drivers/video/fbdev/core/fb_defio.c
> @@ -313,7 +313,7 @@ void fb_deferred_io_open(struct fb_info *info,
>  }
>  EXPORT_SYMBOL_GPL(fb_deferred_io_open);
>
> -void fb_deferred_io_cleanup(struct fb_info *info)
> +void fb_deferred_io_release(struct fb_info *info)
>  {
>         struct fb_deferred_io *fbdefio = info->fbdefio;
>         struct page *page;
> @@ -327,6 +327,14 @@ void fb_deferred_io_cleanup(struct fb_info *info)
>                 page = fb_deferred_io_page(info, i);
>                 page->mapping = NULL;
>         }
> +}
> +EXPORT_SYMBOL_GPL(fb_deferred_io_release);
> +
> +void fb_deferred_io_cleanup(struct fb_info *info)
> +{
> +       struct fb_deferred_io *fbdefio = info->fbdefio;
> +
> +       fb_deferred_io_release(info);
>
>         kvfree(info->pagerefs);
>         mutex_destroy(&fbdefio->lock);
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 3a6c8458eb8d..78c4cb5ee7c9 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1454,6 +1454,8 @@ __releases(&info->lock)
>         struct fb_info * const info = file->private_data;
>
>         lock_fb_info(info);
> +       if (info->fbdefio)
> +               fb_deferred_io_release(info);
>         if (info->fbops->fb_release)
>                 info->fbops->fb_release(info,1);
>         module_put(info->fbops->owner);
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 96b96323e9cb..73eb1f85ea8e 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -662,6 +662,7 @@ extern int  fb_deferred_io_init(struct fb_info *info);
>  extern void fb_deferred_io_open(struct fb_info *info,
>                                 struct inode *inode,
>                                 struct file *file);
> +extern void fb_deferred_io_release(struct fb_info *info);
>  extern void fb_deferred_io_cleanup(struct fb_info *info);
>  extern int fb_deferred_io_fsync(struct file *file, loff_t start,
>                                 loff_t end, int datasync);
> --
> 2.35.3
>