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[PATCH] hw/display/bcm2835_fb.c: Initialize all fields of struct

From: Peter Maydell
Subject: [PATCH] hw/display/bcm2835_fb.c: Initialize all fields of struct
Date: Mon, 12 Oct 2020 16:33:37 +0100

In bcm2835_fb_mbox_push(), Coverity complains (CID 1429989) that we
pass a pointer to a local struct to another function without
initializing all its fields.  This is a real bug:
bcm2835_fb_reconfigure() copies the whole of our new BCM2385FBConfig
struct into s->config, so any fields we don't initialize will corrupt
the state of the device.

Copy the two fields which we don't want to update (pixo and alpha)
from the existing config so we don't accidentally change them.

Fixes: cfb7ba983857e40e88
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Not sure why this wasn't a visible bug -- alpha isn't used,
but if pixo changes from zero to non-zero we flip from
RGB to BGR...
 hw/display/bcm2835_fb.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/display/bcm2835_fb.c b/hw/display/bcm2835_fb.c
index c6263808a27..7c0e5eef2d5 100644
--- a/hw/display/bcm2835_fb.c
+++ b/hw/display/bcm2835_fb.c
@@ -282,6 +282,10 @@ static void bcm2835_fb_mbox_push(BCM2835FBState *s, 
uint32_t value)
     newconf.base = s->vcram_base | (value & 0xc0000000);
     newconf.base += BCM2835_FB_OFFSET;
+    /* Copy fields which we don't want to change from the existing config */
+    newconf.pixo = s->config.pixo;
+    newconf.alpha = s->config.alpha;
     pitch = bcm2835_fb_get_pitch(&newconf);

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