From: James Carlson <carlsonj@workingcode.com>
To: Guillaume Nault <gnault@redhat.com>,
Eric Dumazet <eric.dumazet@gmail.com>
Cc: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, netdev <netdev@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Paul Mackerras <paulus@samba.org>,
linux-ppp@vger.kernel.org, syzbot <syzkaller@googlegroups.com>
Subject: Re: [PATCH net] ppp: ensure minimum packet size in ppp_write()
Date: Wed, 5 Jan 2022 10:30:09 -0500 [thread overview]
Message-ID: <dbde2a45-a7dd-0e8a-d04c-233f69631885@workingcode.com> (raw)
In-Reply-To: <20220105131929.GA17823@pc-1.home>
On 1/5/22 08:19, Guillaume Nault wrote:
> On Wed, Jan 05, 2022 at 03:48:42AM -0800, Eric Dumazet wrote:
>> From: Eric Dumazet <edumazet@google.com>
>>
>> It seems pretty clear ppp layer assumed user space
>> would always be kind to provide enough data
>> in their write() to a ppp device.
>>
>> This patch makes sure user provides at least
>> 2 bytes.
>>
>> It adds PPP_PROTO_LEN macro that could replace
>> in net-next many occurrences of hard-coded 2 value.
>
> The PPP header can be compressed to only 1 byte, but since 2 bytes is
> assumed in several parts of the code, rejecting such packets in
> ppp_xmit() is probably the best we can do.
The only ones that can be compressed are those less than 0x0100, which
are (intentionally) all network layer protocols. We should be getting
only control protocol messages though the user-space interface, not
network layer, so I'd say it's not just the best we can do, but indeed
the right thing to do by design.
--
James Carlson 42.703N 71.076W <carlsonj@workingcode.com>
next prev parent reply other threads:[~2022-01-05 15:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-05 11:48 [PATCH net] ppp: ensure minimum packet size in ppp_write() Eric Dumazet
2022-01-05 13:19 ` Guillaume Nault
2022-01-05 15:30 ` James Carlson [this message]
2022-01-05 16:29 ` Guillaume Nault
2022-01-05 16:35 ` James Carlson
2022-01-05 17:37 ` Guillaume Nault
2022-01-06 12:40 ` patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=dbde2a45-a7dd-0e8a-d04c-233f69631885@workingcode.com \
--to=carlsonj@workingcode.com \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=eric.dumazet@gmail.com \
--cc=gnault@redhat.com \
--cc=kuba@kernel.org \
--cc=linux-ppp@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=paulus@samba.org \
--cc=syzkaller@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).