linux-kernel - Re: [PATCH] EDAC, MCE, AMD: Fix code to prevent NULL dereference

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Date:	Thu, 20 Feb 2014 10:07:33 -0600
From:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
To:	Borislav Petkov <bp@...en8.de>
CC:	<dougthompson@...ssion.com>, <linux-edac@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] EDAC, MCE, AMD: Fix code to prevent NULL dereference

On 2/20/2014 3:32 AM, Borislav Petkov wrote:
> Is that better (I also dropped the "Error Status: " prefix because it is
> not needed):
>
> - [   46.822828] [Hardware Error]: Error Status: Uncorrected, software containable error.
> + [   46.822828] [Hardware Error]: Uncorrected, software containable error.

Okay.

> --
> diff --git a/drivers/edac/mce_amd.c b/drivers/edac/mce_amd.c
> index 30f7309446a6..528b0c4998d9 100644
> --- a/drivers/edac/mce_amd.c
> +++ b/drivers/edac/mce_amd.c
> @@ -741,6 +741,36 @@ int amd_decode_mce(struct notifier_block *nb, unsigned long val, void *data)
>   	if (amd_filter_mce(m))
>   		return NOTIFY_STOP;
>   
> +	pr_emerg(HW_ERR "%s\n", decode_error_status(m));
> +
> +	pr_emerg(HW_ERR "CPU:%d (%x:%x:%x) MC%d_STATUS[%s|%s|%s|%s|%s",
> +		m->extcpu,
> +		c->x86, c->x86_model, c->x86_mask,
> +		m->bank,
> +		((m->status & MCI_STATUS_OVER)	? "Over"  : "-"),
> +		((m->status & MCI_STATUS_UC)	? "UE"	  : "CE"),
> +		((m->status & MCI_STATUS_MISCV)	? "MiscV" : "-"),
> +		((m->status & MCI_STATUS_PCC)	? "PCC"	  : "-"),
> +		((m->status & MCI_STATUS_ADDRV)	? "AddrV" : "-"));
> +
> +	if (c->x86 == 0x15 || c->x86 == 0x16)
> +		pr_cont("|%s|%s",
> +			((m->status & MCI_STATUS_DEFERRED) ? "Deferred" : "-"),
> +			((m->status & MCI_STATUS_POISON)   ? "Poison"   : "-"));
> +
> +	/* do the two bits[14:13] together */
> +	ecc = (m->status >> 45) & 0x3;
> +	if (ecc)
> +		pr_cont("|%sECC", ((ecc == 2) ? "C" : "U"));
> +
> +	pr_cont("]: 0x%016llx\n", m->status);
> +
> +	if (m->status & MCI_STATUS_ADDRV)
> +		pr_emerg(HW_ERR "MC%d_ADDR: 0x%016llx\n", m->bank, m->addr);
> +
> +	if (!fam_ops)
> +		goto err_code;
> +
>   	switch (m->bank) {
>   	case 0:
>   		decode_mc0_mce(m);
> @@ -774,33 +804,7 @@ int amd_decode_mce(struct notifier_block *nb, unsigned long val, void *data)
>   		break;
>   	}
>   
> -	pr_emerg(HW_ERR "Error Status: %s\n", decode_error_status(m));
> -
> -	pr_emerg(HW_ERR "CPU:%d (%x:%x:%x) MC%d_STATUS[%s|%s|%s|%s|%s",
> -		m->extcpu,
> -		c->x86, c->x86_model, c->x86_mask,
> -		m->bank,
> -		((m->status & MCI_STATUS_OVER)	? "Over"  : "-"),
> -		((m->status & MCI_STATUS_UC)	? "UE"	  : "CE"),
> -		((m->status & MCI_STATUS_MISCV)	? "MiscV" : "-"),
> -		((m->status & MCI_STATUS_PCC)	? "PCC"	  : "-"),
> -		((m->status & MCI_STATUS_ADDRV)	? "AddrV" : "-"));
> -
> -	if (c->x86 == 0x15 || c->x86 == 0x16)
> -		pr_cont("|%s|%s",
> -			((m->status & MCI_STATUS_DEFERRED) ? "Deferred" : "-"),
> -			((m->status & MCI_STATUS_POISON)   ? "Poison"   : "-"));
> -
> -	/* do the two bits[14:13] together */
> -	ecc = (m->status >> 45) & 0x3;
> -	if (ecc)
> -		pr_cont("|%sECC", ((ecc == 2) ? "C" : "U"));
> -
> -	pr_cont("]: 0x%016llx\n", m->status);
> -
> -	if (m->status & MCI_STATUS_ADDRV)
> -		pr_emerg(HW_ERR "MC%d_ADDR: 0x%016llx\n", m->bank, m->addr);
> -
> + err_code:
>   	amd_decode_err_code(m->status & 0xffff);
>   
>   	return NOTIFY_STOP;
> @@ -816,10 +820,10 @@ static int __init mce_amd_init(void)
>   	struct cpuinfo_x86 *c = &boot_cpu_data;
>   
>   	if (c->x86_vendor != X86_VENDOR_AMD)
> -		return 0;
> +		return -ENODEV;
>   
>   	if (c->x86 < 0xf || c->x86 > 0x16)
> -		return 0;
> +		return -ENODEV;
>   
>   	fam_ops = kzalloc(sizeof(struct amd_decoder_ops), GFP_KERNEL);
>   	if (!fam_ops)
> @@ -874,6 +878,7 @@ static int __init mce_amd_init(void)
>   	default:
>   		printk(KERN_WARNING "Huh? What family is it: 0x%x?!\n", c->x86);
>   		kfree(fam_ops);
> +		fam_ops = NULL;
>   		return -EINVAL;
>   	}
> --
>

Tested the above a final time on local machine and it works fine..

Thanks,
-Aravind.

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