Messages in this thread Patch in this message | | | From | Michael Thalmeier <> | Subject | [PATCH] mx3fb: fix NULL pointer dereference in screen blanking. | Date | Fri, 23 Sep 2011 14:09:35 +0200 |
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From: Wolfram Stering <wolfram.stering@hale.at>
When blanking an already blanked framebuffer, a kernel NULL pointer dereference occurred, because mx3fb driver handles all kinds of screen blanking (normal, vsync suspend, powerdown) in the same way. Certain programs (Xorg X11 server) first do a normal blank, followed by a powerdown blank, which triggered the bug.
Add an additional safeguard and make sdc_disable_channel() safe against multiple calls independent of other logic.
Signed-off-by: Michael Thalmeier <michael.thalmeier@hale.at> --- drivers/video/mx3fb.c | 13 +++++++++++++ 1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/drivers/video/mx3fb.c b/drivers/video/mx3fb.c index 7e3a490..286be99 100644 --- a/drivers/video/mx3fb.c +++ b/drivers/video/mx3fb.c @@ -382,6 +382,9 @@ static void sdc_disable_channel(struct mx3fb_info *mx3_fbi) uint32_t enabled; unsigned long flags; + if (mx3_fbi->txd == NULL) + return; + spin_lock_irqsave(&mx3fb->lock, flags); enabled = sdc_fb_uninit(mx3_fbi); @@ -986,9 +989,19 @@ static void __blank(int blank, struct fb_info *fbi) { struct mx3fb_info *mx3_fbi = fbi->par; struct mx3fb_data *mx3fb = mx3_fbi->mx3fb; + int was_blank = mx3_fbi->blank; mx3_fbi->blank = blank; + /* Attention! + * Do not call sdc_disable_channel() for a channel that is disabled + * already! This will result in a kernel NULL pointer dereference + * (mx3_fbi->txd is NULL). Hide the fact, that all blank modes are + * handled equally by this driver. + */ + if (blank > FB_BLANK_UNBLANK && was_blank > FB_BLANK_UNBLANK) + return; + switch (blank) { case FB_BLANK_POWERDOWN: case FB_BLANK_VSYNC_SUSPEND: -- 1.7.6.2
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