fix null pointer deref when building against >=libdrm 2.4.78

A new pointer got added to drmEventContext.

As a result of us both:
- Setting drmEventContext.version to "latest" AND
- Not zeroing the struct

We end up thwarting libdrm's compatibility checks, resulting in
libdrm choosing to call through an invalid pointer.

Fix this by zeroing the struct.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/drmmode_display.c b/src/drmmode_display.c
index ae29d9a..2b71c9c 100644
--- a/src/drmmode_display.c
+++ b/src/drmmode_display.c
@@ -1433,7 +1433,7 @@ Bool drmmode_pre_init(ScrnInfoPtr pScrn, int fd, int cpp)
 	unsigned int crtcs_needed = 0;
 	int crtcshift;
 
-	drmmode = xnfalloc(sizeof *drmmode);
+	drmmode = xnfcalloc(sizeof(*drmmode), 1);
 	drmmode->fd = fd;
 	drmmode->fb_id = 0;