[PATCH v2 net-next] ipv4: fib: fix route re-dump in inet_dump_fib() on multi-batch dump
From: Pengfei Zhang <hidden>
Date: 2026-06-30 08:42:28
Also in:
lkml
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
inet_dump_fib() saves its progress in cb->args[1] as a positional
index within the current hash chain. Between batches, a concurrent
fib_new_table() can insert a new table at the chain head, shifting
all existing entries. On resume the saved index lands on a different
table, causing already-dumped tables to be re-dumped and the
originally suspended table to restart from the beginning.
Fix by storing tb->tb_id in cb->args[1] instead of a positional
index, mirroring the fix applied to inet6_dump_fib() in commit
9facb861dc6b ("ipv6: fib6: fix NULL deref in fib6_walk_continue()
on multi-batch dump").
Signed-off-by: Pengfei Zhang <redacted>
---
v2:
- Drop Fixes tag (not needed for net-next)
- Fix variable declaration order (reverse xmas tree)
- Reference IPv6 fix commit hash
v1: https://lore.kernel.org/netdev/20260626085636.1524451-1-zhangfeionline@gmail.com/ (local)
net/ipv4/fib_frontend.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 42212970d..248895e7e 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c@@ -1019,10 +1019,11 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) .dump_routes = true, .dump_exceptions = true, }; - unsigned int e = 0, s_e, h, s_h; struct hlist_head *head; int dumped = 0, err = 0; struct fib_table *tb; + unsigned int h, s_h; + u32 s_id; rcu_read_lock(); if (cb->strict_check) {
@@ -1054,29 +1055,28 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) } s_h = cb->args[0]; - s_e = cb->args[1]; + s_id = cb->args[1]; err = 0; - for (h = s_h; h < FIB_TABLE_HASHSZ; h++, s_e = 0) { - e = 0; + for (h = s_h; h < FIB_TABLE_HASHSZ; h++, s_id = 0) { head = &net->ipv4.fib_table_hash[h]; hlist_for_each_entry_rcu(tb, head, tb_hlist) { - if (e < s_e) - goto next; + if (s_id && tb->tb_id != s_id) + continue; + + s_id = 0; if (dumped) memset(&cb->args[2], 0, sizeof(cb->args) - 2 * sizeof(cb->args[0])); + cb->args[1] = tb->tb_id; err = fib_table_dump(tb, skb, cb, &filter); if (err < 0) goto out; dumped = 1; -next: - e++; } } out: - cb->args[1] = e; cb->args[0] = h; unlock:
--
2.54.0