From 6c71cfcc01685ef495ca7886471a76e73446424e Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Fri, 21 Aug 2020 20:34:07 +1000 Subject: [PATCH] powerpc/prom_init: Check display props exist before enabling btext It's possible to enable CONFIG_PPC_EARLY_DEBUG_BOOTX for a pseries kernel (maybe it shouldn't be), which is then booted with qemu/slof. But if you do that the kernel crashes in draw_byte(), with a DAR pointing somewhere near INT_MAX. Adding some debug to prom_init we see that we're not able to read the "address" property from OF, so we're just using whatever junk value was on the stack. So check the properties can be read properly from OF, if not we bail out before initialising btext, which avoids the crash. Signed-off-by: Michael Ellerman Reviewed-by: Alexey Kardashevskiy Link: https://lore.kernel.org/r/20200821103407.3362149-1-mpe@ellerman.id.au --- arch/powerpc/kernel/prom_init.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c index ae7ec9903191..5090a5ab54e5 100644 --- a/arch/powerpc/kernel/prom_init.c +++ b/arch/powerpc/kernel/prom_init.c @@ -2422,10 +2422,19 @@ static void __init prom_check_displays(void) u32 width, height, pitch, addr; prom_printf("Setting btext !\n"); - prom_getprop(node, "width", &width, 4); - prom_getprop(node, "height", &height, 4); - prom_getprop(node, "linebytes", &pitch, 4); - prom_getprop(node, "address", &addr, 4); + + if (prom_getprop(node, "width", &width, 4) == PROM_ERROR) + return; + + if (prom_getprop(node, "height", &height, 4) == PROM_ERROR) + return; + + if (prom_getprop(node, "linebytes", &pitch, 4) == PROM_ERROR) + return; + + if (prom_getprop(node, "address", &addr, 4) == PROM_ERROR) + return; + prom_printf("W=%d H=%d LB=%d addr=0x%x\n", width, height, pitch, addr); btext_setup_display(width, height, 8, pitch, addr);