netdev - Re: send/sendmsg ENOMEM errors WAS(Re: [PATCH net 6/6] sctp: not return ENOMEM err back in sctp_packet

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: <2fa21505-59c2-fb8b-6e89-11fccc953d25@mojatatu.com>
Date:   Sun, 23 Oct 2016 15:52:08 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Vlad Yasevich <vyasevic@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
        Michael Tuexen <Michael.Tuexen@...chi.franken.de>,
        Eric Dumazet <edumazet@...gle.com>,
        Brenda Butler <bjb@...atatu.com>, gabor@...atatu.com
Subject: Re: send/sendmsg ENOMEM errors WAS(Re: [PATCH net 6/6] sctp: not
 return ENOMEM err back in sctp_packet_transmit

On 16-10-23 02:20 PM, Xin Long wrote:

> This patch doesn't ignore all the ENOMEN cases, only after msg is
> enqueued in out queue/send queue, in the lower layer, when alloc
> new skb and copy data from old skb, if it fails to alloc new skb, sctp
> will ignore this ENOMEM, as this msg will be taken care by retransmit
> mechanism, it's reasonable and also safe, user can't feel that.
>

Yes, that part i got.

> But for the cases before enqueue, like in sctp_sendmsg,
> sctp_datamsg_from_user may return ENOMEM, this err will return
> back to user, and can't be ignored.
>

The hard part is distinguishing between the above case and real
failure.
I am assuming in the case above user is _not_ required to send
again. But in the general case they are required to send again.
Correct?

> So I don't really think we should change something in manpage, what
> do you think ? maybe a little explanation there is also nice, :)

Yes, that would help. In particular it should be clear what user space
is expected to do. While this is about sctp - I am assuming equivalent
behavior for all callers of sendxxx() regardless of protocol.

cheers,
jamal