netdev - Re: [RFC] Zero-length write() does not generate a datagram on connected socket

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <46FAA936.6040205@hp.com>
Date:	Wed, 26 Sep 2007 14:47:18 -0400
From:	Vlad Yasevich <vladislav.yasevich@...com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Stephen Hemminger <shemminger@...ux-foundation.org>,
	netdev@...r.kernel.org
Subject: Re: [RFC] Zero-length write() does not generate a datagram on connected
 socket

Herbert Xu wrote:
> Stephen Hemminger <shemminger@...ux-foundation.org> wrote:
>> The bug http://bugzilla.kernel.org/show_bug.cgi?id=5731
>> describes an issue where write() can't be used to generate a zero-length
>> datagram (but send, and sendto do work).
>>
>> I think the following is needed:
>>
>> --- a/net/socket.c      2007-08-20 09:54:28.000000000 -0700
>> +++ b/net/socket.c      2007-09-24 15:31:25.000000000 -0700
>> @@ -777,8 +777,11 @@ static ssize_t sock_aio_write(struct kio
>>        if (pos != 0)
>>                return -ESPIPE;
>>
>> -       if (iocb->ki_left == 0) /* Match SYS5 behaviour */
>> -               return 0;
>> +       if (unlikely(iocb->ki_left == 0)) {
>> +               struct socket *sock = iocb->ki_filp->private_data;
>> +               if (sock->type == SOCK_STREAM)
>> +                       return 0;
>> +       }
> 
> I'm not sure whether all STREAM protocols treat zero-length
> sends as no-ops.  What about SCTP?

0 byte writes are not allowed in SCTP.  A no-op is fine, otherwise
SCTP would return an error.

-vlad

> 
> Put it another way, do we really need to keep the short-circuit
> for SOCK_STREAM?
> 
> Cheers,

-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html