admin/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-07 20:06:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

neighbour: Convert RTM_SETNEIGHTBL to RCU.

Browse Source 
neightbl_set() fetches neigh_tables[] and updates attributes under
write_lock_bh(&tbl->lock), so RTNL is not needed.

neigh_table_clear() synchronises RCU only, and rcu_dereference_rtnl()
protects nothing here.

If we released RCU after fetching neigh_tables[], there would be no
synchronisation to block neigh_table_clear() further, so RCU is held
until the end of the function.

Another option would be to protect neigh_tables[] user with SRCU
and add synchronize_srcu() in neigh_table_clear().

But, holding RCU should be fine as we hold write_lock_bh() for the
rest of neightbl_set() anyway.

Let's perform RTM_SETNEIGHTBL under RCU and drop RTNL.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251022054004.2514876-5-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2025-10-22 05:39:48 +00:00
committed by Jakub Kicinski
parent 4ae34be500
commit 55a6046b48
1 changed files with 14 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
net/core/neighbour.c
View File

@@ -2362,9 +2362,9 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
struct net *net = sock_net(skb->sk);
struct nlattr *tb[NDTA_MAX + 1];
struct neigh_table *tbl;
struct ndtmsg *ndtmsg;
struct nlattr *tb[NDTA_MAX+1];
bool found = false;
int err, tidx;
@@ -2380,20 +2380,27 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh,
ndtmsg = nlmsg_data(nlh);
rcu_read_lock();
for (tidx = 0; tidx < NEIGH_NR_TABLES; tidx++) {
tbl = rcu_dereference_rtnl(neigh_tables[tidx]);
tbl = rcu_dereference(neigh_tables[tidx]);
if (!tbl)
continue;
if (ndtmsg->ndtm_family && tbl->family != ndtmsg->ndtm_family)
continue;
if (nla_strcmp(tb[NDTA_NAME], tbl->id) == 0) {
found = true;
break;
}
}
if (!found)
return -ENOENT;
if (!found) {
rcu_read_unlock();
err = -ENOENT;
goto errout;
}
/*
* We acquire tbl->lock to be nice to the periodic timers and
@@ -2519,6 +2526,7 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh,
errout_tbl_lock:
write_unlock_bh(&tbl->lock);
rcu_read_unlock();
errout:
return err;
}
@@ -3909,7 +3917,8 @@ static const struct rtnl_msg_handler neigh_rtnl_msg_handlers[] __initconst = {
.flags = RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED},
{.msgtype = RTM_GETNEIGHTBL, .dumpit = neightbl_dump_info,
.flags = RTNL_FLAG_DUMP_UNLOCKED},
{.msgtype = RTM_SETNEIGHTBL, .doit = neightbl_set},
{.msgtype = RTM_SETNEIGHTBL, .doit = neightbl_set,
.flags = RTNL_FLAG_DOIT_UNLOCKED},
};
static int __init neigh_init(void)