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ipmr: Convert ipmr_rtm_dumplink() to RCU.

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net->ipv4.mr_tables is updated under RTNL and can be read
safely under RCU.

Once created, the multicast route tables are not removed
until netns dismantle.

ipmr_rtm_dumplink() does not need RTNL protection for
ipmr_for_each_table() and ipmr_fill_table() if RCU is held.

Even if mrt->maxvif changes concurrently, ipmr_fill_vif()
returns true to continue dumping the next table.

Let's convert it to RCU.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260228221800.1082070-4-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2026-02-28 22:17:21 +00:00 committed by Jakub Kicinski
parent 261950e039
commit 402a8111d7
1 changed files with 17 additions and 12 deletions
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29
net/ipv4/ipmr.c
View File

@ -2901,12 +2901,13 @@ static bool ipmr_fill_table(struct mr_table *mrt, struct sk_buff *skb)
if (nla_put_u32(skb, IPMRA_TABLE_ID, mrt->id) ||
nla_put_u32(skb, IPMRA_TABLE_CACHE_RES_QUEUE_LEN, queue_len) ||
nla_put_s32(skb, IPMRA_TABLE_MROUTE_REG_VIF_NUM,
mrt->mroute_reg_vif_num) ||
READ_ONCE(mrt->mroute_reg_vif_num)) ||
nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_ASSERT,
mrt->mroute_do_assert) ||
nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_PIM, mrt->mroute_do_pim) ||
READ_ONCE(mrt->mroute_do_assert)) ||
nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_PIM,
READ_ONCE(mrt->mroute_do_pim)) ||
nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_WRVIFWHOLE,
mrt->mroute_do_wrvifwhole))
READ_ONCE(mrt->mroute_do_wrvifwhole)))
return false;
return true;
@ -2919,7 +2920,7 @@ static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb)
struct vif_device *vif;
vif = &mrt->vif_table[vifid];
vif_dev = rtnl_dereference(vif->dev);
vif_dev = vif_dev_read(vif);
/* if the VIF doesn't exist just continue */
if (!vif_dev)
return true;
@ -2928,16 +2929,16 @@ static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb)
if (!vif_nest)
return false;
if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, vif_dev->ifindex) ||
if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, READ_ONCE(vif_dev->ifindex)) ||
nla_put_u32(skb, IPMRA_VIFA_VIF_ID, vifid) ||
nla_put_u16(skb, IPMRA_VIFA_FLAGS, vif->flags) ||
nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_IN, vif->bytes_in,
nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_IN, READ_ONCE(vif->bytes_in),
IPMRA_VIFA_PAD) ||
nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_OUT, vif->bytes_out,
nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_OUT, READ_ONCE(vif->bytes_out),
IPMRA_VIFA_PAD) ||
nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_IN, vif->pkt_in,
nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_IN, READ_ONCE(vif->pkt_in),
IPMRA_VIFA_PAD) ||
nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_OUT, vif->pkt_out,
nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_OUT, READ_ONCE(vif->pkt_out),
IPMRA_VIFA_PAD) ||
nla_put_be32(skb, IPMRA_VIFA_LOCAL_ADDR, vif->local) ||
nla_put_be32(skb, IPMRA_VIFA_REMOTE_ADDR, vif->remote)) {
@ -2992,6 +2993,8 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb)
s_t = cb->args[0];
s_e = cb->args[1];
rcu_read_lock();
ipmr_for_each_table(mrt, net) {
struct nlattr *vifs, *af;
struct ifinfomsg *hdr;
@ -3026,7 +3029,7 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb)
nlmsg_end(skb, nlh);
goto out;
}
for (i = 0; i < mrt->maxvif; i++) {
for (i = 0; i < READ_ONCE(mrt->maxvif); i++) {
if (e < s_e)
goto skip_entry;
if (!ipmr_fill_vif(mrt, i, skb)) {
@ -3048,6 +3051,8 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb)
}
out:
rcu_read_unlock();
cb->args[1] = e;
cb->args[0] = t;
@ -3287,7 +3292,7 @@ static struct pernet_operations ipmr_net_ops = {
static const struct rtnl_msg_handler ipmr_rtnl_msg_handlers[] __initconst = {
{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_GETLINK,
.dumpit = ipmr_rtm_dumplink},
.dumpit = ipmr_rtm_dumplink, .flags = RTNL_FLAG_DUMP_UNLOCKED},
{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_NEWROUTE,
.doit = ipmr_rtm_route},
{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_DELROUTE,