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Message-ID: <20230821145933.98511-1-kuniyu@amazon.com> Date: Mon, 21 Aug 2023 07:59:33 -0700 From: Kuniyuki Iwashima <kuniyu@...zon.com> To: <jrife@...gle.com> CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>, <netdev@...r.kernel.org>, <pabeni@...hat.com>, <kuniyu@...zon.com> Subject: Re: [PATCH] net: Avoid address overwrite in kernel_connect From: Jordan Rife <jrife@...gle.com> Date: Mon, 21 Aug 2023 05:00:06 -0500 > BPF programs that run on connect can rewrite the connect address. For > the connect system call this isn't a problem, because a copy of the address > is made when it is moved into kernel space. However, kernel_connect > simply passes through the address it is given, so the caller may observe > its address value unexpectedly change. > > A practical example where this is problematic is where NFS is combined > with a system such as Cilium which implements BPF-based load balancing. > A common pattern in software-defined storage systems is to have an NFS > mount that connects to a persistent virtual IP which in turn maps to an > ephemeral server IP. This is usually done to achieve high availability: > if your server goes down you can quickly spin up a replacement and remap > the virtual IP to that endpoint. With BPF-based load balancing, mounts > will forget the virtual IP address when the address rewrite occurs > because a pointer to the only copy of that address is passed down the > stack. Server failover then breaks, because clients have forgotten the > virtual IP address. Reconnects fail and mounts remain broken. This patch > was tested by setting up a scenario like this and ensuring that NFS > reconnects worked after applying the patch. > > Signed-off-by: Jordan Rife <jrife@...gle.com> > --- > net/socket.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/net/socket.c b/net/socket.c > index 2b0e54b2405c8..f49edb9b49185 100644 > --- a/net/socket.c > +++ b/net/socket.c > @@ -3519,7 +3519,11 @@ EXPORT_SYMBOL(kernel_accept); > int kernel_connect(struct socket *sock, struct sockaddr *addr, int addrlen, > int flags) > { > - return sock->ops->connect(sock, addr, addrlen, flags); > + struct sockaddr_storage address; > + > + memcpy(&address, addr, addrlen); > + > + return sock->ops->connect(sock, (struct sockaddr *)&address, addrlen, flags); Could you rebase on net-next.git ? I think this patch conflicts with 1ded5e5a5931 ("net: annotate data-races around sock->ops"). > } > EXPORT_SYMBOL(kernel_connect); > > -- > 2.42.0.rc1.204.g551eb34607-goog
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