From: Eric Dumazet <eric.dumazet@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: "David S. Miller" <davem@davemloft.net>,
Alexander Potapenko <glider@google.com>,
Kostya Serebryany <kcc@google.com>,
Andrey Konovalov <andreyknvl@google.com>,
Eric Dumazet <edumazet@google.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
security@kernel.org
Subject: Re: [PATCH] net: recvmsg: Unconditionally zero struct sockaddr_storage
Date: Tue, 31 Oct 2017 10:31:34 -0700 [thread overview]
Message-ID: <1509471094.3828.26.camel@edumazet-glaptop3.roam.corp.google.com> (raw)
In-Reply-To: <20171031161445.GA140874@beast>
On Tue, 2017-10-31 at 09:14 -0700, Kees Cook wrote:
> Some protocols do not correctly wipe the contents of the on-stack
> struct sockaddr_storage sent down into recvmsg() (e.g. SCTP), and leak
> kernel stack contents to userspace. This wipes it unconditionally before
> per-protocol handlers run.
>
> Note that leaks like this are mitigated by building with
> CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL=y
>
> Reported-by: Alexander Potapenko <glider@google.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> net/socket.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/socket.c b/net/socket.c
> index c729625eb5d3..34183f4fbdf8 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2188,6 +2188,7 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
> struct sockaddr __user *uaddr;
> int __user *uaddr_len = COMPAT_NAMELEN(msg);
>
> + memset(&addr, 0, sizeof(addr));
> msg_sys->msg_name = &addr;
>
This kind of patch comes every year.
Standard answer is : We fix the buggy protocol, we do not make
everything slower just because we are lazy.
struct sockaddr is 128 bytes, but IPV4 only uses a fraction of it.
Also memset() is using long word stores, so next 4-byte or 2-byte stores
on same location hit a performance problem on x86.
By adding all these defensive programming, we would give strong
incentives to bypass the kernel for networking. That would be bad.
next prev parent reply other threads:[~2017-10-31 17:31 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-31 16:14 [PATCH] net: recvmsg: Unconditionally zero struct sockaddr_storage Kees Cook
2017-10-31 17:31 ` Eric Dumazet [this message]
2017-11-01 12:48 ` Eric W. Biederman
2017-11-01 18:23 ` Kees Cook
2017-11-15 8:22 ` Alexander Potapenko
2017-11-16 4:17 ` [PATCH net] net/sctp: Always set scope_id in sctp_inet6_skb_msgname Eric W. Biederman
2017-11-16 14:00 ` David Miller
2017-11-15 2:13 ` [PATCH] net: recvmsg: Unconditionally zero struct sockaddr_storage Kees Cook
2017-11-15 18:37 ` Eric W. Biederman
2017-10-31 17:35 ` Ben Hutchings
2017-11-01 6:49 ` Willy Tarreau
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=1509471094.3828.26.camel@edumazet-glaptop3.roam.corp.google.com \
--to=eric.dumazet@gmail.com \
--cc=andreyknvl@google.com \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=glider@google.com \
--cc=kcc@google.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=security@kernel.org \
/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).