On 11/4/24 11:25 PM, Kees Cook wrote:
> Instead of a heap allocation use a stack allocated sockaddr_storage to
> support arbitrary length addr_len value (but bounds check it against the
> maximum address length).
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> net/core/rtnetlink.c | 12 ++++--------
> 1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index f0a520987085..eddd10b74f06 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -2839,21 +2839,17 @@ static int do_setlink(const struct sk_buff *skb,
> }
>
> if (tb[IFLA_ADDRESS]) {
> - struct sockaddr *sa;
> - int len;
> + struct sockaddr_storage addr;
> + struct sockaddr *sa = (struct sockaddr *)&addr;
We already use too much stack space.
Please move addr into struct rtnl_newlink_tbs ?
>
> - len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
> - sizeof(*sa));
> - sa = kmalloc(len, GFP_KERNEL);
> - if (!sa) {
> + if (dev->addr_len > sizeof(addr.__data)) {
> err = -ENOMEM;
> goto errout;
> }
> sa->sa_family = dev->type;
> - memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
> + memcpy(addr.__data, nla_data(tb[IFLA_ADDRESS]),
> dev->addr_len);
> err = dev_set_mac_address_user(dev, sa, extack);
> - kfree(sa);
> if (err)
> goto errout;
> status |= DO_SETLINK_MODIFIED;