GNU bug report logs - #45595
recvfrom! optional start and end parameter invalid

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: d4ryus <d4ryus <at> mailbox.org>
To: bug-guile <at> gnu.org
Subject: recvfrom! optional start and end parameter invalid
Date: Fri, 1 Jan 2021 12:34:57 +0100

[Message part 1 (text/plain, inline)]

hi,

the parameter validation for the optional "start" and "end" arguments to
"recvfrom!" are off by one if "end" is passed. From libguile/socket.c
(master commit 64c89458e6):

  ...
  if (SCM_UNBNDP (end))
    cend = SCM_BYTEVECTOR_LENGTH (buf);
  else
    {
      cend = scm_to_size_t (end);
      if (SCM_UNLIKELY (cend >= SCM_BYTEVECTOR_LENGTH (buf)
                        || cend < offset))
        scm_out_of_range (FUNC_NAME, end);
    }
  ...

"end" is the optional end argument, "offset" is 0 or "start" if start
was given. The check must be:

  cend > SCM_BYTEVECTOR_LENGTH (buf) || cend <= offset

to allow filling the last byte in the buffer and verify that start is
not equal to end. A workaround to skip the validation is to not pass
end. But i think a better way would be to always validate start (and
end), if one (or both) of them are passed. A potentional fix is
attached.

If you need any additional information, please let me know.

Thank you for your great work!

-  d4ryus

[recvfrom-fix.patch (text/plain, attachment)]

Message #10 received at 45595-done <at> debbugs.gnu.org (full text, mbox):

From: lloda <lloda <at> sarc.name>
To: 45595-done <at> debbugs.gnu.org
Subject: Re: recvfrom! optional start and end parameter invalid
Date: Wed, 3 Nov 2021 19:29:03 +0100

Hi,

Your patch didn't allow for start == end, which is valid as far as I can tell.

With that amended, applied in 1a8294f495cb202f8fcd0f260627c58e7a4c4d10. Thanks!

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