netdev - Re: [PATCH 1/1] net:socket: set msg_namelen to 0 if msg_name is passed as NULL in msghdr struct from userland.

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Date:	Tue, 9 Sep 2014 15:14:06 -0700
From:	Ani Sinha <ani@...sta.com>
To:	Ani Sinha <ani@...sta.com>, fruggeri <fruggeri@...sta.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	fenner <fenner@...sta.com>, travisb <travisb@...sta.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	"matthew.leach" <matthew.leach@....com>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH 1/1] net:socket: set msg_namelen to 0 if msg_name is
 passed as NULL in msghdr struct from userland.

Any feedback on this patch? Any concerns?

On Mon, Sep 8, 2014 at 2:49 PM, Ani Sinha <ani@...sta.com> wrote:
> Linux manpage for recvmsg and sendmsg calls does not explicitly mention setting msg_namelen to 0 when
> msg_name passed set as NULL. When developers don't set msg_namelen member in msghdr, it might contain garbage
> value which will fail the validation check and sendmsg and recvmsg calls from kernel will return EINVAL. This will
> break old binaries and any code for which there is no access to source code.
> To fix this, we set msg_namelen to 0 when msg_name is passed as NULL from userland.
>
> Signed-off-by: Ani Sinha <ani@...sta.com>
> ---
>  net/socket.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/net/socket.c b/net/socket.c
> index 95ee7d8..457be6a 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -1997,6 +1997,9 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
>         if (copy_from_user(kmsg, umsg, sizeof(struct msghdr)))
>                 return -EFAULT;
>
> +       if (kmsg->msg_name == NULL)
> +               kmsg->msg_namelen = 0;
> +
>         if (kmsg->msg_namelen < 0)
>                 return -EINVAL;
>
> --
> 1.7.4.4
>
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