netdev - Re: Fw: [Bug 205681] New: recvmg is overwriting the buffer passed in msg_name by exceeding msg

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Message-ID: <CA+FuTSeBmuk0OOG_Psmj-WGz6njWDEpFLnwsUHUAMHjuc3a-rg@mail.gmail.com>
Date:   Wed, 27 Nov 2019 12:13:40 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Network Development <netdev@...r.kernel.org>
Subject: Re: Fw: [Bug 205681] New: recvmg is overwriting the buffer passed in
 msg_name by exceeding msg_namelen

On Wed, Nov 27, 2019 at 11:09 AM Stephen Hemminger
<stephen@...workplumber.org> wrote:
>
>
>
> Begin forwarded message:
>
> Date: Wed, 27 Nov 2019 06:36:50 +0000
> From: bugzilla-daemon@...zilla.kernel.org
> To: stephen@...workplumber.org
> Subject: [Bug 205681] New: recvmg is overwriting the buffer passed in msg_name by exceeding msg_namelen
>
>
> https://bugzilla.kernel.org/show_bug.cgi?id=205681
>
>             Bug ID: 205681
>            Summary: recvmg is overwriting the buffer passed in msg_name by
>                     exceeding msg_namelen
>            Product: Networking
>            Version: 2.5
>     Kernel Version: 5.4,4.0,3.0,2.6
>           Hardware: All
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: high
>           Priority: P1
>          Component: IPV4
>           Assignee: stephen@...workplumber.org
>           Reporter: sudheendrasp@...il.com
>         Regression: No
>
> if (msg->msg_name) {
>         struct sockaddr_rxrpc *srx = msg->msg_name;
>         size_t len = sizeof(call->peer->srx);
>
>         memcpy(msg->msg_name, &call->peer->srx, len);
>         srx->srx_service = call->service_id;
>         msg->msg_namelen = len;
>     }
>
>
> As seen, recvmsg is doing memcpy of len which can be greater than msg_namelen
> passed.

__sys_recvfrom in net/socket.c always passes a struct of size
sockaddr_storage to the protocol handler. On return from the protocol
handler it calls move_addr_to_user to safely copy up to msg_namelen
only.