Re: [PATCH net v3] rtnetlink: let rtnl_bridge_setlink checks IFLA_BRIDGE_MODE length

[Hangbin Liu <liuhangbin@gmail.com>]

On Wed, Jul 26, 2023 at 03:53:14PM +0800, Lin Ma wrote:
> There are totally 9 ndo_bridge_setlink handlers in the current kernel,
> which are 1) bnxt_bridge_setlink, 2) be_ndo_bridge_setlink 3)
> i40e_ndo_bridge_setlink 4) ice_bridge_setlink 5)
> ixgbe_ndo_bridge_setlink 6) mlx5e_bridge_setlink 7)
> nfp_net_bridge_setlink 8) qeth_l2_bridge_setlink 9) br_setlink.
> 
> By investigating the code, we find that 1-7 parse and use nlattr
> IFLA_BRIDGE_MODE but 3 and 4 forget to do the nla_len check. This can
> lead to an out-of-attribute read and allow a malformed nlattr (e.g.,
> length 0) to be viewed as a 2 byte integer.
> 
> To avoid such issues, also for other ndo_bridge_setlink handlers in the
> future. This patch adds the nla_len check in rtnl_bridge_setlink and
> does an early error return if length mismatches. To make it works, the
> break is removed from the parsing for IFLA_BRIDGE_FLAGS to make sure
> this nla_for_each_nested iterates every attribute.
> 
> Fixes: b1edc14a3fbf ("ice: Implement ice_bridge_getlink and ice_bridge_setlink")
> Fixes: 51616018dd1b ("i40e: Add support for getlink, setlink ndo ops")
> Suggested-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: Lin Ma <linma@zju.edu.cn>
> Acked-by: Nikolay Aleksandrov <razor@blackwall.org>

Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>