From: Al Viro
> > I think the problem with wmnet is not that it was expecting the fields
> > to be aligned because it never had problems before (when definitely more
> > than 10 megabytes were received, wmnet is crappy but not _that_ crappy).
> >
> > I think the problem really was here,
> >
> > totalbytes_in = strtoul(&buffer[7], NULL, 10);
> >
> > After the patch the device name is 8 characters long and &buffer[7]
> > overlaps with the name instead of reading the bytes. Before the
> > patch is was fine because the call to strtoul() seems correct in the
> > sense that it would read everything until the NULL. So more than 10
> > megabytes was still ok.
> >
> > So I guess I was wrong when suggesting that the problem was the
> > alignment.
>
> Several lines below there's this:
> totalpackets_out = strtoul(&buffer[74], NULL, 10);
> if (totalpackets_out != lastpackets_out) {
> totalbytes_out = strtoul(&buffer[66], NULL,
> 10);
> diffpackets_out += totalpackets_out -
> lastpackets_out;
> diffbytes_out += totalbytes_out -
> lastbytes_out;
> lastpackets_out = totalpackets_out;
> lastbytes_out = totalbytes_out;
> tx = True;
> }
>
> So I'm afraid it *is* that crappy. This function really should use scanf();
> note that updateStats_ipchains() in the same file does just that (well,
> fgets()+sscanf() for fsck knows what reason). And I'd be careful with all
> those %d, actually - it's not _that_ hard to get more than 4Gb sent.
> scanf formats really ought to match the kernel-side (seq_)printf one...
IMHO it is safer to use strchr(p, ' '); to skip the interface name and then
use repeated calls to strtoull() to read the numbers.
Correctly/safely using scanf() is really too hard.
David
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