[fwts PATCH v2 1/1] lib: enable /dev/mem access on aarch64

[Heinrich Schuchardt]

On 15.10.20 20:01, Leif Lindholm wrote:
> On Thu, Oct 15, 2020 at 18:42:54 +0200, Heinrich Schuchardt wrote:
>> The SMBIOS3 table supplied by U-Boot cannot be read without mmap.
>
> In order to access SMBIOS on anything other than pre-UEFI x86 systems,
> linux should be built with CONFIG_DMI_SYSFS
>
> /dev/mem is the opposite of what operating systems are for, and
> enabling it on any ARM system leads to trivial (and frequently
> accidental) denial-of-service attacks from userland.
>
> /
>     Leif

I fully understand your security concerns. But given a kernel that
exposes /dev/mem is there any reason for fwts not to use it?

I based my v5.9 kernel on arm64 defconfig. The defconfig has
CONFIG_DMI_SYSFS=n, CONFIG_DEVMEM=y. The Debian v5.8 kernel has
CONFIG_DMI_SYSFS=y, CONFIG_DEVMEM=y.

Best regards

Heinrich

>
>> Cc: Leif Lindholm <leif at nuviainc.com>
>> Fixes: f36ff824d145 ("lib: disable /dev/mem access on aarch64")
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>> ---
>> v2:
>> 	Leif's email address has changed
>> ---
>>  src/lib/include/fwts.h | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/src/lib/include/fwts.h b/src/lib/include/fwts.h
>> index 6f13d262..a4163055 100644
>> --- a/src/lib/include/fwts.h
>> +++ b/src/lib/include/fwts.h
>> @@ -105,6 +105,7 @@
>>  #define FWTS_ARCH_AARCH64	1
>>  #define FWTS_HAS_ACPI	1
>>  #define FWTS_HAS_UEFI	1
>> +#define FWTS_USE_DEVMEM 1
>>  #endif
>>
>>  #if defined(__s390x__)
>> --
>> 2.28.0
>>