[PATCH] soc: renesas: Add missing check for non-zero product register address

[PATCH] soc: renesas: Add missing check for non-zero product register address

[Geert Uytterhoeven]

If the DTB for a device with an RZ/A2 SoC lacks a device node for the
BSID register, the ID validation code falls back to using a register at
address 0x0, which leads to undefined behavior (e.g. reading back a
random value).

This could be fixed by letting fam_rza2.reg point to the actual BSID
register.  However, the hardcoded fallbacks were meant for backwards
compatibility with old DTBs only, not for new SoCs.  Hence fix this by
validating renesas_family.reg before using it.

Fixes: 175f435f44b724e3 ("soc: renesas: identify RZ/A2")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/soc/renesas/renesas-soc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/soc/renesas/renesas-soc.c b/drivers/soc/renesas/renesas-soc.c
index 5dc2ae55f746a48a..85aaf85ce6b192d9 100644
--- a/drivers/soc/renesas/renesas-soc.c
+++ b/drivers/soc/renesas/renesas-soc.c
@@ -337,7 +337,7 @@ static int __init renesas_soc_init(void)
 	if (np) {
 		chipid = of_iomap(np, 0);
 		of_node_put(np);
-	} else if (soc->id) {
+	} else if (soc->id && family->reg) {
 		chipid = ioremap(family->reg, 4);
 	}
 	if (chipid) {
-- 
2.17.1

Re: [PATCH] soc: renesas: Add missing check for non-zero product register address

[Geert Uytterhoeven]

On Wed, Oct 16, 2019 at 4:33 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
> If the DTB for a device with an RZ/A2 SoC lacks a device node for the
> BSID register, the ID validation code falls back to using a register at
> address 0x0, which leads to undefined behavior (e.g. reading back a
> random value).
>
> This could be fixed by letting fam_rza2.reg point to the actual BSID
> register.  However, the hardcoded fallbacks were meant for backwards
> compatibility with old DTBs only, not for new SoCs.  Hence fix this by
> validating renesas_family.reg before using it.
>
> Fixes: 175f435f44b724e3 ("soc: renesas: identify RZ/A2")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Queuing in renesas-devel for v5.5.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds