panic: invalid bcd xxx

[Eric van Gyzen]

On 02/28/2017 16:57, Conrad Meyer wrote:
> On Tue, Feb 28, 2017 at 2:31 PM, Eric van Gyzen <vangyzen at freebsd.org> wrote:
>> Your system's real-time clock is returning garbage.  r312702 added some
>> input validation a few weeks ago.  Previously, the kernel was reading beyond
>> the end of an array and either complaining about the clock or setting it to
>> the wrong time based on whatever was in the memory beyond the array.
>>
>> The added validation shouldn't be an assertion because it operates on data
>> beyond the kernel's control.  Try this:
>>
>> --- sys/libkern.h       (revision 314424)
>> +++ sys/libkern.h       (working copy)
>> @@ -57,8 +57,10 @@
>>  bcd2bin(int bcd)
>>  {
>>
>> -       KASSERT(bcd >= 0 && bcd < LIBKERN_LEN_BCD2BIN,
>> -           ("invalid bcd %d", bcd));
>> +       if (bcd < 0 || bcd >= LIBKERN_LEN_BCD2BIN) {
>> +               printf("invalid bcd %d\n", bcd);
>> +               return (0);
>> +       }
>>         return (bcd2bin_data[bcd]);
>>  }
>
> I don't think removing this assertion and truncating to zero is the
> right thing to do.  Adding an error return to this routine is a little
> much, though.  I think probably the caller should perform input
> validation between the broken device and this routine.

Either of those would be a much better solution.  This was just a quick 
hack to get the memstick to boot.

Eric