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rtnetlink: do_setlink: Use struct sockaddr_storage

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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.

Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20250521204619.2301870-7-kees@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kees Cook
2025-05-21 13:46:15 -07:00
committed by Paolo Abeni
parent 9ca6804ab7
commit 6b12e0a3c3
1 changed files with 4 additions and 15 deletions
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19
net/core/rtnetlink.c
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@@ -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;