| Message ID | 20250520223108.2672023-7-kees@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | net: Convert dev_set_mac_address() to struct sockaddr_storage | expand |
On 20/05/25 16:31, Kees Cook wrote: > 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 <kees@kernel.org> Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org> Thanks! -Gustavo > --- > Cc: Kuniyuki Iwashima <kuniyu@amazon.com> > Cc: Eric Dumazet <edumazet@google.com> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Paolo Abeni <pabeni@redhat.com> > Cc: Simon Horman <horms@kernel.org> > Cc: Ido Schimmel <idosch@nvidia.com> > Cc: <netdev@vger.kernel.org> > --- > 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;
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;
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 <kees@kernel.org> --- Cc: Kuniyuki Iwashima <kuniyu@amazon.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Simon Horman <horms@kernel.org> Cc: Ido Schimmel <idosch@nvidia.com> Cc: <netdev@vger.kernel.org> --- net/core/rtnetlink.c | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-)