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netkit: no longer rely on RTNL in netkit_fill_info()

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netkit_fill_info() used rtnl_dereference() to fetch nk->peer,
and thus required RTNL.

nk->peer is already an RCU protected pointer, updated with
rcu_assign_pointer() and read from the fast path with
rcu_dereference(). Simply use rcu_dereference() under
rcu_read_lock() instead.

While at it, use READ_ONCE() when reading nk->policy, because
netkit_change_link() can change it at any time (it already uses
WRITE_ONCE()).

Other fields (primary, mode, pair, scrub) are only set from
netkit_new_link(), before the device is visible to dumps.

Also add missing const qualifiers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260916111953.1611574-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-09-16 11:19:53 +00:00 committed by Jakub Kicinski
parent 8050e0efd4
commit aea70e81be
1 changed files with 11 additions and 6 deletions
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17
drivers/net/netkit.c
View File

@ -1209,12 +1209,12 @@ static size_t netkit_get_size(const struct net_device *dev)
static int netkit_fill_info(struct sk_buff *skb, const struct net_device *dev)
{
struct netkit *nk = netkit_priv(dev);
struct net_device *peer = rtnl_dereference(nk->peer);
const struct netkit *nk = netkit_priv(dev);
const struct net_device *peer;
if (nla_put_u8(skb, IFLA_NETKIT_PRIMARY, nk->primary))
return -EMSGSIZE;
if (nla_put_u32(skb, IFLA_NETKIT_POLICY, nk->policy))
if (nla_put_u32(skb, IFLA_NETKIT_POLICY, READ_ONCE(nk->policy)))
return -EMSGSIZE;
if (nla_put_u32(skb, IFLA_NETKIT_MODE, nk->mode))
return -EMSGSIZE;
@ -1228,13 +1228,18 @@ static int netkit_fill_info(struct sk_buff *skb, const struct net_device *dev)
if (nla_put_u32(skb, IFLA_NETKIT_PAIRING, nk->pair))
return -EMSGSIZE;
rcu_read_lock();
peer = rcu_dereference(nk->peer);
if (peer) {
nk = netkit_priv(peer);
if (nla_put_u32(skb, IFLA_NETKIT_PEER_POLICY, nk->policy))
return -EMSGSIZE;
if (nla_put_u32(skb, IFLA_NETKIT_PEER_SCRUB, nk->scrub))
if (nla_put_u32(skb, IFLA_NETKIT_PEER_POLICY,
READ_ONCE(nk->policy)) ||
nla_put_u32(skb, IFLA_NETKIT_PEER_SCRUB, nk->scrub)) {
rcu_read_unlock();
return -EMSGSIZE;
}
}
rcu_read_unlock();
return 0;
}