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net: bridge: prevent too big nested attributes in br_fill_linkxstats()

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After commit ff205bf8c554 ("netlink: add one debug check in nla_nest_end()")
syzbot found that br_fill_linkxstats() can send corrupted netlink packets.

Make sure the nested attribute size is bounded.

Fixes: a60c090361 ("bridge: netlink: export per-vlan stats")
Reported-by: syzbot+a35f9259d08f907c06e6@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6a0b0da3.050a0220.175f0c.0000.GAE@google.com/
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260520114207.1394241-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-05-20 11:42:07 +00:00 committed by Jakub Kicinski
parent 979c017803
commit bdd39576bf
2 changed files with 13 additions and 2 deletions
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10
net/bridge/br_netlink.c
View File

@ -1824,6 +1824,7 @@ static int br_fill_linkxstats(struct sk_buff *skb,
const struct net_device *dev,
int *prividx, int attr)
{
unsigned int limit = U16_MAX - nla_total_size(0);
struct nlattr *nla __maybe_unused;
struct net_bridge_port *p = NULL;
struct net_bridge_vlan_group *vg;
@ -1841,6 +1842,7 @@ static int br_fill_linkxstats(struct sk_buff *skb,
p = br_port_get_rtnl(dev);
if (!p)
return 0;
limit -= nla_total_size_64bit(sizeof(p->stp_xstats));
br = p->br;
vg = nbp_vlan_group(p);
break;
@ -1855,6 +1857,9 @@ static int br_fill_linkxstats(struct sk_buff *skb,
if (vg) {
u16 pvid;
#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
limit -= nla_total_size_64bit(sizeof(struct br_mcast_stats));
#endif
pvid = br_get_pvid(vg);
list_for_each_entry(v, &vg->vlan_list, vlist) {
struct bridge_vlan_xstats vxi;
@ -1862,6 +1867,11 @@ static int br_fill_linkxstats(struct sk_buff *skb,
if (++vl_idx < *prividx)
continue;
if (skb_tail_pointer(skb) - (unsigned char *)nest +
nla_total_size(sizeof(vxi)) >= limit)
goto nla_put_failure;
memset(&vxi, 0, sizeof(vxi));
vxi.vid = v->vid;
vxi.flags = v->flags;

5
net/core/rtnetlink.c
View File

@ -6328,8 +6328,9 @@ static int rtnl_stats_get(struct sk_buff *skb, struct nlmsghdr *nlh,
NETLINK_CB(skb).portid, nlh->nlmsg_seq, 0,
0, &filters, &idxattr, &prividx, extack);
if (err < 0) {
/* -EMSGSIZE implies BUG in if_nlmsg_stats_size */
WARN_ON(err == -EMSGSIZE);
/* -EMSGSIZE implies BUG in if_nlmsg_stats_size
* or a too big nested attribute.
*/
kfree_skb(nskb);
} else {
err = rtnl_unicast(nskb, net, NETLINK_CB(skb).portid);