Re: [PATCH net] selinux: add the missing walk_size + len check in selinux_sctp_bind_connect

[Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>]

On Sat, Mar 09, 2019 at 12:07:34AM +0800, Xin Long wrote:
> As does in __sctp_connect(), when checking addrs in a while loop, after
> get the addr len according to sa_family, it's necessary to do the check
> walk_size + af->sockaddr_len > addrs_size to make sure it won't access
> an out-of-bounds addr.
> 
> The same thing is needed in selinux_sctp_bind_connect(), otherwise an
> out-of-bounds issue can be triggered:
> 
>   [14548.772313] BUG: KASAN: slab-out-of-bounds in selinux_sctp_bind_connect+0x1aa/0x1f0
>   [14548.927083] Call Trace:
>   [14548.938072]  dump_stack+0x9a/0xe9
>   [14548.953015]  print_address_description+0x65/0x22e
>   [14548.996524]  kasan_report.cold.6+0x92/0x1a6
>   [14549.015335]  selinux_sctp_bind_connect+0x1aa/0x1f0
>   [14549.036947]  security_sctp_bind_connect+0x58/0x90
>   [14549.058142]  __sctp_setsockopt_connectx+0x5a/0x150 [sctp]
>   [14549.081650]  sctp_setsockopt.part.24+0x1322/0x3ce0 [sctp]
> 
> Fixes: d452930fd3b9 ("selinux: Add SCTP support")
> Reported-by: Chunyu Hu <chuhu@redhat.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Paul, how can we get this into -stable trees? SELinux process may be
different from -net trees.

> ---
>  security/selinux/hooks.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index f0e36c3..dac9bdb 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5120,6 +5120,9 @@ static int selinux_sctp_bind_connect(struct sock *sk, int optname,
>  			return -EINVAL;
>  		}
>  
> +		if (walk_size + len > addrlen)
> +			return -EINVAL;
> +
>  		err = -EINVAL;
>  		switch (optname) {
>  		/* Bind checks */
> -- 
> 2.1.0
>