Re: [PATCH v2] fbdev: Fix invalid page access after closing deferred I/O devices
From: Thomas Zimmermann <tzimmermann@suse.de>
Date: 2023-01-30 08:28:46
Also in:
dri-devel, lkml
Hi Am 29.01.23 um 09:28 schrieb 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.
Do you have more information on this problem? The mmap'ed buffer of the fbdev device comes from a vmalloc call. That memory's location never changes; even across pairs of open/close on the device file. I'm surprised that a page entry becomes invalid. In drm_fbdev_cleanup(), we first remove the fbdefio at [1] and then vfree() the shadow buffer. So the memory should still be around until fbdevio is gone. [1] https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_fb_helper.c#L2146
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().
The delayed work is required to copy the framebuffer to the device output. So if it's just canceled, could this result in missing updates? There's a call to cancel_delayed_work_sync() in the new helper fb_deferred_io_release(). Is this the right function? Maybe flush_delayed_work() is a better choice.
Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com> Cc: <redacted> Signed-off-by: Takashi Iwai <redacted>
This could use a Fixes tag. It's not exactly clear to me when this
problem got originally introduced, but the recent refactoring seems a
candidate.
Fixes: 56c134f7f1b5 ("fbdev: Track deferred-I/O pages in pageref struct")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Zack Rusin <redacted>
Cc: VMware Graphics Reviewers <redacted>
Cc: Jaya Kumar <jayalk@intworks.biz>
Cc: Daniel Vetter <redacted>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Steve Glendinning <steve.glendinning@shawell.net>
Cc: Bernie Thompson <bernie@plugable.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Stephen Kitt <redacted>
Cc: Peter Suti <redacted>
Cc: Sam Ravnborg <redacted>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: ye xingchen <redacted>
Cc: Petr Mladek <pmladek@suse.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Tom Rix <trix@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Cc: linux-hyperv@vger.kernel.org
Cc: <redacted> # v5.19+
quoted hunk ↗ jump to hunk
--- v1->v2: Fix build error without CONFIG_FB_DEFERRED_IO drivers/video/fbdev/core/fb_defio.c | 10 +++++++++- drivers/video/fbdev/core/fbmem.c | 4 ++++ include/linux/fb.h | 1 + 3 files changed, 14 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);
It's all in the same module. No need to export this symbol. Best regards Thomas
quoted hunk ↗ jump to hunk
+ +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..ab3545a00abc 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c@@ -1454,6 +1454,10 @@ __releases(&info->lock) struct fb_info * const info = file->private_data; lock_fb_info(info); +#if IS_ENABLED(CONFIG_FB_DEFERRED_IO) + if (info->fbdefio) + fb_deferred_io_release(info); +#endif if (info->fbops->fb_release) info->fbops->fb_release(info,1);
quoted hunk ↗ jump to hunk
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);
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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