Re: [PATCH] ACPI / extlog: don't dereference extlog_l1_addr if it is null

[Borislav Petkov <bp@alien8.de>]

CCing authors too.

On Wed, Dec 02, 2015 at 11:58:28AM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> There is a check to see if extlog_l1_addr is null before calling
> acpi_os_unmap_iomem, however, before that call there is a
> dereference on this that could trip an oops.  Move the
> extlog_l1_addr dereference so it occurs only if it is not null.
> 
> Found by static analysis by smatch.
> 
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/acpi/acpi_extlog.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
> index b3842ff..183b7b2 100644
> --- a/drivers/acpi/acpi_extlog.c
> +++ b/drivers/acpi/acpi_extlog.c
> @@ -309,9 +309,10 @@ static void __exit extlog_exit(void)
>  {
>  	set_edac_report_status(old_edac_report_status);
>  	mce_unregister_decode_chain(&extlog_mce_dec);
> -	((struct extlog_l1_head *)extlog_l1_addr)->flags &= ~FLAG_OS_OPTIN;
> -	if (extlog_l1_addr)
> +	if (extlog_l1_addr) {
> +		((struct extlog_l1_head *)extlog_l1_addr)->flags &= ~FLAG_OS_OPTIN;
>  		acpi_os_unmap_iomem(extlog_l1_addr, l1_size);
> +	}
>  	if (elog_addr)
>  		acpi_os_unmap_iomem(elog_addr, elog_size);
>  	release_mem_region(elog_base, elog_size);
> -- 
> 2.6.2
> 
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-- 
Regards/Gruss,
    Boris.

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