net: reduce rtnetlink_rcv_msg() stack usage

IFLA_MAX is increasing slowly but surely.

Some compilers use more than 512 bytes of stack in rtnetlink_rcv_msg()
because it calls rtnl_calcit() for RTM_GETLINK message.

Use noinline_for_stack attribute to not inline rtnl_calcit(),
and directly use nla_for_each_attr_type() (Jakub suggestion)
because we only care about IFLA_EXT_MASK at this stage.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240710151653.3786604-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index eabfc8290f5e29f2ef3e5c1481715ae9056ea689..87e67194f24046a8420bbb51c19fb0a686b9b06b 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3969,22 +3969,28 @@ static int rtnl_dellinkprop(struct sk_buff *skb, struct nlmsghdr *nlh,
        return rtnl_linkprop(RTM_DELLINKPROP, skb, nlh, extack);
 }
 
-static u32 rtnl_calcit(struct sk_buff *skb, struct nlmsghdr *nlh)
+static noinline_for_stack u32 rtnl_calcit(struct sk_buff *skb,
+                                         struct nlmsghdr *nlh)
 {
        struct net *net = sock_net(skb->sk);
        size_t min_ifinfo_dump_size = 0;
-       struct nlattr *tb[IFLA_MAX+1];
        u32 ext_filter_mask = 0;
        struct net_device *dev;
-       int hdrlen;
+       struct nlattr *nla;
+       int hdrlen, rem;
 
        /* Same kernel<->userspace interface hack as in rtnl_dump_ifinfo. */
        hdrlen = nlmsg_len(nlh) < sizeof(struct ifinfomsg) ?
                 sizeof(struct rtgenmsg) : sizeof(struct ifinfomsg);
 
-       if (nlmsg_parse_deprecated(nlh, hdrlen, tb, IFLA_MAX, ifla_policy, NULL) >= 0) {
-               if (tb[IFLA_EXT_MASK])
-                       ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]);
+       if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
+               return NLMSG_GOODSIZE;
+
+       nla_for_each_attr_type(nla, IFLA_EXT_MASK,
+                              nlmsg_attrdata(nlh, hdrlen),
+                              nlmsg_attrlen(nlh, hdrlen), rem) {
+               if (nla_len(nla) == sizeof(u32))
+                       ext_filter_mask = nla_get_u32(nla);
        }
 
        if (!ext_filter_mask)