[PATCH] ARM: davinci: da850-evm: Avoid NULL pointer dereference

[Bartosz Golaszewski]

On Thu, Dec 23, 2021 at 11:22 PM Nathan Chancellor <nathan at kernel.org> wrote:
>
> With newer versions of GCC, there is a panic in da850_evm_config_emac()
> when booting multi_v5_defconfig in QEMU under the palmetto-bmc machine:
>
> Unable to handle kernel NULL pointer dereference at virtual address 00000020
> pgd = (ptrval)
> [00000020] *pgd=00000000
> Internal error: Oops: 5 [#1] PREEMPT ARM
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper Not tainted 5.15.0 #1
> Hardware name: Generic DT based system
> PC is at da850_evm_config_emac+0x1c/0x120
> LR is at do_one_initcall+0x50/0x1e0
>
> The emac_pdata pointer in soc_info is NULL because davinci_soc_info only
> gets populated on davinci machines but da850_evm_config_emac() is called
> on all machines via device_initcall().
>
> Move the rmii_en assignment below the machine check so that it is only
> dereferenced when running on a supported SoC.
>
> Cc: stable at vger.kernel.org
> Fixes: bae105879f2f ("davinci: DA850/OMAP-L138 EVM: implement autodetect of RMII PHY")
> Link: https://lore.kernel.org/r/YcS4xVWs6bQlQSPC@archlinux-ax161/
> Reviewed-by: Arnd Bergmann <arnd at arndb.de>
> Signed-off-by: Nathan Chancellor <nathan at kernel.org>
> ---
>  arch/arm/mach-davinci/board-da850-evm.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-davinci/board-da850-evm.c b/arch/arm/mach-davinci/board-da850-evm.c
> index 428012687a80..7f7f6bae21c2 100644
> --- a/arch/arm/mach-davinci/board-da850-evm.c
> +++ b/arch/arm/mach-davinci/board-da850-evm.c
> @@ -1101,11 +1101,13 @@ static int __init da850_evm_config_emac(void)
>         int ret;
>         u32 val;
>         struct davinci_soc_info *soc_info = &davinci_soc_info;
> -       u8 rmii_en = soc_info->emac_pdata->rmii_en;
> +       u8 rmii_en;
>
>         if (!machine_is_davinci_da850_evm())
>                 return 0;
>
> +       rmii_en = soc_info->emac_pdata->rmii_en;
> +
>         cfg_chip3_base = DA8XX_SYSCFG0_VIRT(DA8XX_CFGCHIP3_REG);
>
>         val = __raw_readl(cfg_chip3_base);
>
> base-commit: a7904a538933c525096ca2ccde1e60d0ee62c08e
> --
> 2.34.1
>

Reviewed-by: Bartosz Golaszewski <brgl at bgdev.pl>