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neighbour: Convert RTM_GETNEIGHTBL to RCU.

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neightbl_dump_info() calls these functions for each neigh_tables[]
entry:

  1. neightbl_fill_info() for tbl->parms
  2. neightbl_fill_param_info() for tbl->parms_list (except tbl->parms)

Both functions rely on the table lock (read_lock_bh(&tbl->lock))
and RTNL is not needed.

Let's fetch the table under RCU and convert RTM_GETNEIGHTBL to RCU.

Note that the first entry of tbl->parms_list is tbl->parms.list and
embedded in neigh_table, so list_next_entry() is safe.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251022054004.2514876-4-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2025-10-22 05:39:47 +00:00
committed by Jakub Kicinski
parent 35d7c70870
commit 4ae34be500
1 changed files with 9 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
net/core/neighbour.c
View File

@@ -2176,7 +2176,7 @@ static int neightbl_fill_parms(struct sk_buff *skb, struct neigh_parms *parms)
return -ENOBUFS;
if ((parms->dev &&
nla_put_u32(skb, NDTPA_IFINDEX, parms->dev->ifindex)) ||
nla_put_u32(skb, NDTPA_IFINDEX, READ_ONCE(parms->dev->ifindex))) ||
nla_put_u32(skb, NDTPA_REFCNT, refcount_read(&parms->refcnt)) ||
nla_put_u32(skb, NDTPA_QUEUE_LENBYTES,
NEIGH_VAR(parms, QUEUE_LEN_BYTES)) ||
@@ -2228,8 +2228,6 @@ static int neightbl_fill_info(struct sk_buff *skb, struct neigh_table *tbl,
return -EMSGSIZE;
ndtmsg = nlmsg_data(nlh);
read_lock_bh(&tbl->lock);
ndtmsg->ndtm_family = tbl->family;
ndtmsg->ndtm_pad1 = 0;
ndtmsg->ndtm_pad2 = 0;
@@ -2255,11 +2253,9 @@ static int neightbl_fill_info(struct sk_buff *skb, struct neigh_table *tbl,
.ndtc_proxy_qlen = READ_ONCE(tbl->proxy_queue.qlen),
};
rcu_read_lock();
nht = rcu_dereference(tbl->nht);
ndc.ndtc_hash_rnd = nht->hash_rnd[0];
ndc.ndtc_hash_mask = ((1 << nht->hash_shift) - 1);
rcu_read_unlock();
if (nla_put(skb, NDTA_CONFIG, sizeof(ndc), &ndc))
goto nla_put_failure;
@@ -2297,12 +2293,10 @@ static int neightbl_fill_info(struct sk_buff *skb, struct neigh_table *tbl,
if (neightbl_fill_parms(skb, &tbl->parms) < 0)
goto nla_put_failure;
read_unlock_bh(&tbl->lock);
nlmsg_end(skb, nlh);
return 0;
nla_put_failure:
read_unlock_bh(&tbl->lock);
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
}
@@ -2321,8 +2315,6 @@ static int neightbl_fill_param_info(struct sk_buff *skb,
return -EMSGSIZE;
ndtmsg = nlmsg_data(nlh);
read_lock_bh(&tbl->lock);
ndtmsg->ndtm_family = tbl->family;
ndtmsg->ndtm_pad1 = 0;
ndtmsg->ndtm_pad2 = 0;
@@ -2331,11 +2323,9 @@ static int neightbl_fill_param_info(struct sk_buff *skb,
neightbl_fill_parms(skb, parms) < 0)
goto errout;
read_unlock_bh(&tbl->lock);
nlmsg_end(skb, nlh);
return 0;
errout:
read_unlock_bh(&tbl->lock);
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
}
@@ -2575,10 +2565,12 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
family = ((struct rtgenmsg *)nlmsg_data(nlh))->rtgen_family;
rcu_read_lock();
for (tidx = 0; tidx < NEIGH_NR_TABLES; tidx++) {
struct neigh_parms *p;
tbl = rcu_dereference_rtnl(neigh_tables[tidx]);
tbl = rcu_dereference(neigh_tables[tidx]);
if (!tbl)
continue;
@@ -2592,7 +2584,7 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
nidx = 0;
p = list_next_entry(&tbl->parms, list);
list_for_each_entry_from(p, &tbl->parms_list, list) {
list_for_each_entry_from_rcu(p, &tbl->parms_list, list) {
if (!net_eq(neigh_parms_net(p), net))
continue;
@@ -2612,6 +2604,8 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
neigh_skip = 0;
}
out:
rcu_read_unlock();
cb->args[0] = tidx;
cb->args[1] = nidx;
@@ -3913,7 +3907,8 @@ static const struct rtnl_msg_handler neigh_rtnl_msg_handlers[] __initconst = {
{.msgtype = RTM_DELNEIGH, .doit = neigh_delete},
{.msgtype = RTM_GETNEIGH, .doit = neigh_get, .dumpit = neigh_dump_info,
.flags = RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED},
{.msgtype = RTM_GETNEIGHTBL, .dumpit = neightbl_dump_info},
{.msgtype = RTM_GETNEIGHTBL, .dumpit = neightbl_dump_info,
.flags = RTNL_FLAG_DUMP_UNLOCKED},
{.msgtype = RTM_SETNEIGHTBL, .doit = neightbl_set},
};