[Interest] [PATCH qtbase] qlinuxfbscreen: fix crash in switchToGraphicsMode()

[Thomas Petazzoni]

The switchToGraphicsMode() function calls the KDGETMODE ioctl() call,
but passes the address of oldMode, which is already a
pointer. Therefore, the current code makes the kernel write the "mode"
value returned by the KDGETMODE ioctl() at the address of the oldMode
pointer. This pointer becomes NULL, which makes the following line
trigger a segfault.

Since the function already receives as argument the address of
oldMode, there is no need to do &oldMode when doing the ioctl() call.

This patch fixes the following segfault:

Program received signal SIGSEGV, Segmentation fault.
0x768acc40 in switchToGraphicsMode (oldMode=0x0, ttyfd=7) at qlinuxfbscreen.cpp:268
268	       if (*oldMode != KD_GRAPHICS) {
(gdb) bt

Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
---
 src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp b/src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp
index 1dac60a..4d170f1 100644
--- a/src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp
+++ b/src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp
@@ -264,7 +264,7 @@ static int openTtyDevice(const QString &device)
 
 static bool switchToGraphicsMode(int ttyfd, int *oldMode)
 {
-    ioctl(ttyfd, KDGETMODE, &oldMode);
+    ioctl(ttyfd, KDGETMODE, oldMode);
     if (*oldMode != KD_GRAPHICS) {
        if (ioctl(ttyfd, KDSETMODE, KD_GRAPHICS) != 0)
             return false;
-- 
1.7.9.5