Re: Problems with miss-behaving uBlox Module

[Gary E. Miller]

Yo Andreas!

On Tue, 30 Mar 2021 04:58:45 +0000
Neustifter Andreas <Andreas.Neustifter@kapsch.net> wrote:

> > I added a check in packet.c for a u-blox packet with a length field
> > containing zero.  Now in git head.  It could not go into an
> > infinite loop, but it possibly could have looped a long time.  
> 
> Yes, this is what I have done in the interim as well but wanted to
> verify it first. Good to know that you came to the same conclusion.

Nothing verified until I have a data sample that used to fail.

> Philosophical topic: since lexer->length is a (unsigned) size_t I
> think the else branch will never be executed. In this case: do you
> prefer leaving the else in there, just in case or remove it (and
> maybe add a comment?).

I think you are talking about this code:

        if (0 == lexer->length) {
            // no payload
            lexer->state = UBX_CHECKSUM_A;
        } else if (MAX_PACKET_LENGTH >= lexer->length) {
            // normal size payload
            lexer->state = UBX_LENGTH_2;
        } else {
            // bad length
            return character_pushback(lexer, GROUND_STATE);
        }

In that case the else can happen if the length is too long.  Coverity
is pretty fussy about having tests like that.

> The information contained in this e-mail message is privileged and
> confidential and is for the exclusive use of the addressee.

Fat chance.

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
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