From owner-freebsd-current@freebsd.org  Tue Feb 28 23:16:04 2017
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Subject: Re: panic: invalid bcd xxx
To: cem@freebsd.org
References: <20170228224739.167f2273@bsd64.grem.de>
 <226a00fa-5d04-0aa7-e0cc-6078edde6639@FreeBSD.org>
 <CAG6CVpXGQds1NYOOd1trYBTE8KNm=VYA3mq9yK3gjjVMt3NNpA@mail.gmail.com>
Cc: Michael Gmelin <freebsd@grem.de>,
 "freebsd-current@freebsd.org" <freebsd-current@freebsd.org>
From: Eric van Gyzen <vangyzen@FreeBSD.org>
Message-ID: <b753effa-aa7f-ff20-d127-28e1e827f304@FreeBSD.org>
Date: Tue, 28 Feb 2017 17:16:02 -0600
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On 02/28/2017 16:57, Conrad Meyer wrote:
> On Tue, Feb 28, 2017 at 2:31 PM, Eric van Gyzen <vangyzen@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