Instead of a heap allocating a variably sized struct sockaddr and lying about the type in the call to netif_set_mac_address(), use a stack allocated struct sockaddr_storage. This lets us drop the cast and avoid the allocation.
Putting "ss" on the stack means it will get a reused stack slot since it is the same size (128B) as other existing single-scope stack variables, like the vfinfo array (128B), so no additional stack space is used by this function. Signed-off-by: Kees Cook <[email protected]> --- Cc: Kuniyuki Iwashima <[email protected]> Cc: Eric Dumazet <[email protected]> Cc: Jakub Kicinski <[email protected]> Cc: "David S. Miller" <[email protected]> Cc: Paolo Abeni <[email protected]> Cc: Simon Horman <[email protected]> Cc: Ido Schimmel <[email protected]> Cc: <[email protected]> --- net/core/rtnetlink.c | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 9743f1c2ae3c..f9a35bdc58ad 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -3080,17 +3080,7 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev, } if (tb[IFLA_ADDRESS]) { - struct sockaddr *sa; - int len; - - len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len, - sizeof(*sa)); - sa = kmalloc(len, GFP_KERNEL); - if (!sa) { - err = -ENOMEM; - goto errout; - } - sa->sa_family = dev->type; + struct sockaddr_storage ss = { }; netdev_unlock_ops(dev); @@ -3098,10 +3088,9 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev, down_write(&dev_addr_sem); netdev_lock_ops(dev); - memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]), - dev->addr_len); - err = netif_set_mac_address(dev, (struct sockaddr_storage *)sa, extack); - kfree(sa); + ss.ss_family = dev->type; + memcpy(ss.__data, nla_data(tb[IFLA_ADDRESS]), dev->addr_len); + err = netif_set_mac_address(dev, &ss, extack); if (err) { up_write(&dev_addr_sem); goto errout; -- 2.34.1
