Patch "ipv6: properly combine dev_base_seq and ipv6.dev_addr_genid" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ipv6: properly combine dev_base_seq and ipv6.dev_addr_genid

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ipv6-properly-combine-dev_base_seq-and-ipv6.dev_addr.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 0085fffe948ea0730c0e4d0be2c7bfcba7784698
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Thu Feb 15 17:21:07 2024 +0000

    ipv6: properly combine dev_base_seq and ipv6.dev_addr_genid
    
    [ Upstream commit e898e4cd1aab271ca414f9ac6e08e4c761f6913c ]
    
    net->dev_base_seq and ipv6.dev_addr_genid are monotonically increasing.
    
    If we XOR their values, we could miss to detect if both values
    were changed with the same amount.
    
    Fixes: 63998ac24f83 ("ipv6: provide addr and netconf dump consistency info")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Cc: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
    
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Acked-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 79787a1f5ab34..150c2f71ec89f 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -698,6 +698,22 @@ static int inet6_netconf_get_devconf(struct sk_buff *in_skb,
 	return err;
 }
 
+/* Combine dev_addr_genid and dev_base_seq to detect changes.
+ */
+static u32 inet6_base_seq(const struct net *net)
+{
+	u32 res = atomic_read(&net->ipv6.dev_addr_genid) +
+		  net->dev_base_seq;
+
+	/* Must not return 0 (see nl_dump_check_consistent()).
+	 * Chose a value far away from 0.
+	 */
+	if (!res)
+		res = 0x80000000;
+	return res;
+}
+
+
 static int inet6_netconf_dump_devconf(struct sk_buff *skb,
 				      struct netlink_callback *cb)
 {
@@ -731,8 +747,7 @@ static int inet6_netconf_dump_devconf(struct sk_buff *skb,
 		idx = 0;
 		head = &net->dev_index_head[h];
 		rcu_read_lock();
-		cb->seq = atomic_read(&net->ipv6.dev_addr_genid) ^
-			  net->dev_base_seq;
+		cb->seq = inet6_base_seq(net);
 		hlist_for_each_entry_rcu(dev, head, index_hlist) {
 			if (idx < s_idx)
 				goto cont;
@@ -5288,7 +5303,7 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 	}
 
 	rcu_read_lock();
-	cb->seq = atomic_read(&tgt_net->ipv6.dev_addr_genid) ^ tgt_net->dev_base_seq;
+	cb->seq = inet6_base_seq(tgt_net);
 	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
 		idx = 0;
 		head = &tgt_net->dev_index_head[h];