Commit 2bd6c9d6 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Jakub Kicinski
Browse files

ipmr: Use MAXVIFS in mroute_msgsize(). 



mroute_msgsize() calculates skb size needed for ipmr_fill_mroute().

The size differs based on mrt->maxvif.

We will drop RTNL for ipmr_rtm_getroute() and mrt->maxvif may
change under RCU.

To avoid -EMSGSIZE, let's calculate the size with the maximum
value of mrt->maxvif, MAXVIFS.

struct rtnexthop is 8 bytes and MAXVIFS is 32, so the maximum delta
is 256 bytes, which is small enough.

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260228221800.1082070-5-kuniyu@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 402a8111

net/ipv4/ipmr.c

+4 −5
Original line number Diff line number Diff line
@@ -2510,7 +2510,7 @@ static int _ipmr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb, 
				cmd, flags);

}



static size_t mroute_msgsize(bool unresolved, int maxvif)

static size_t mroute_msgsize(bool unresolved)

{

	size_t len =

		NLMSG_ALIGN(sizeof(struct rtmsg))
@@ -2523,7 +2523,7 @@ static size_t mroute_msgsize(bool unresolved, int maxvif) 
		len = len

		      + nla_total_size(4)	/* RTA_IIF */

		      + nla_total_size(0)	/* RTA_MULTIPATH */

		      + maxvif * NLA_ALIGN(sizeof(struct rtnexthop))

		      + MAXVIFS * NLA_ALIGN(sizeof(struct rtnexthop))

						/* RTA_MFC_STATS */

		      + nla_total_size_64bit(sizeof(struct rta_mfc_stats))

		;
@@ -2538,8 +2538,7 @@ static void mroute_netlink_event(struct mr_table *mrt, struct mfc_cache *mfc, 
	struct sk_buff *skb;

	int err = -ENOBUFS;



	skb = nlmsg_new(mroute_msgsize(mfc->_c.mfc_parent >= MAXVIFS,

				       mrt->maxvif),

	skb = nlmsg_new(mroute_msgsize(mfc->_c.mfc_parent >= MAXVIFS),

			GFP_ATOMIC);

	if (!skb)

		goto errout;
@@ -2711,7 +2710,7 @@ static int ipmr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh, 
		goto errout_free;

	}



	skb = nlmsg_new(mroute_msgsize(false, mrt->maxvif), GFP_KERNEL);

	skb = nlmsg_new(mroute_msgsize(false), GFP_KERNEL);

	if (!skb) {

		err = -ENOBUFS;

		goto errout_free;