netfilter: nft_fib_ipv6: walk fib6_siblings under RCU

nft_fib6_info_nh_uses_dev() runs from nft_fib6_eval() in softirq under
rcu_read_lock().  fib6_siblings is modified by writers that hold
tb6_lock but do not wait for RCU readers, so the sibling walk should
use list_for_each_entry_rcu(): it adds READ_ONCE() on the ->next
pointer and lets CONFIG_PROVE_RCU_LIST validate the locking.

No functional change for non-debug builds.

Fixes: 1c32b24c234b ("netfilter: nft_fib_ipv6: switch to fib6_lookup")
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Florian Westphal <fw@strlen.de>

diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
index 8b2dba88ee96d318781df70e7c09d80b0fc4e23f..5e192a446ec82518ff9a28e86dae8c5db8542d86 100644 (file)
--- a/net/ipv6/netfilter/nft_fib_ipv6.c
+++ b/net/ipv6/netfilter/nft_fib_ipv6.c
@@ -170,7 +170,7 @@ static bool nft_fib6_info_nh_uses_dev(struct fib6_info *rt,
        if (nft_fib6_info_nh_dev_match(nh_dev, dev))
                return true;
 
-       list_for_each_entry(iter, &rt->fib6_siblings, fib6_siblings) {
+       list_for_each_entry_rcu(iter, &rt->fib6_siblings, fib6_siblings) {
                nh_dev = fib6_info_nh_dev(iter);
 
                if (nft_fib6_info_nh_dev_match(nh_dev, dev))