From: Wolfram Stering <wolfram.stering@xxxxxxx>
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@xxxxxxx>
---
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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