Re: [PATCH net] net: pktgen: reject out-of-range node indices

[Daehyeon Ko <4ncienth@gmail.com>]

Hi Simon,

Thanks for reviewing.

1. I checked all 32 num_arg() call sites. Its unchecked accumulation
   also wraps on 32-bit for ten-digit values, including count and delay,
   and several destinations narrow to int or u16. I did not find another
   direct unbounded bitmap lookup among these callers. This is not a
   claim that the other conversions are safe; I have not demonstrated
   another OOB there.

2. kstrtoint() can handle all valid node IDs, with an explicit
   0 <= node < MAX_NUMNODES check before node_possible().
   A direct kstrtoint_from_user() replacement is stricter than num_arg():
   for example, it rejects trailing spaces, whereas num_arg() accepts a
   decimal prefix. kstrtouint() would also need the bitmap range check.

   I propose keeping the existing ten-digit decimal lexer and using
   kstrtoint(..., 10, ...) for conversion, retaining the existing ERROR
   result and write count. This removes the duplicate accumulator and
   prevents 32-bit wrap. A host comparison against the pinned parsers
   passed; this alternative has not yet been built or run as a kernel
   patch.

3. Reducing maxlen alone does not enforce the bitmap bound. It also
   truncates rather than rejects excess digits, so reducing it to nine
   changes valid zero-padded node arguments.

Regards,
Daehyeon