ARM: davinci: da850-evm: Avoid NULL pointer dereference

BugLink: https://bugs.launchpad.net/bugs/1969857
commit 83a1cde5c74bfb44b49cb2a940d044bb2380f4ea upstream.

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.

Fixes: bae105879f2f ("davinci: DA850/OMAP-L138 EVM: implement autodetect of RMII PHY")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/YcS4xVWs6bQlQSPC@archlinux-ax161/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/arm/mach-davinci/board-da850-evm.c b/arch/arm/mach-davinci/board-da850-evm.c
index 428012687a802a9f2cbeeb9e24f950e5bd5f960f..7f7f6bae21c2d7dd0ffb8f17e58b9fb5ea25cb47 100644 (file)
--- 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);