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Subject[PATCH 5.4 032/104] ipv4: Detect rollover in specific fib table dump
From: David Ahern <>

[ Upstream commit 9827c0634e461703abf81e8cc8b7adf5da5886d0 ]

Sven-Haegar reported looping on fib dumps when route has
been added to a table. The looping is caused by the key rolling over from
FFFFFFFF to 0. When dumping a specific table only, we need a means to detect
when the table dump is done. The key and count saved to cb args are both 0
only at the start of the table dump. If key is 0 and count > 0, then we are
in the rollover case. Detect and return to avoid looping.

This only affects dumps of a specific table; for dumps of all tables
(the case prior to the change in the Fixes tag) inet_dump_fib moved
the entry counter to the next table and reset the cb args used by
fib_table_dump and fn_trie_dump_leaf, so the rollover ffffffff back
to 0 did not cause looping with the dumps.

Fixes: effe67926624 ("net: Enable kernel side filtering of route dumps")
Reported-by: Sven-Haegar Koch <>
Signed-off-by: David Ahern <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>
net/ipv4/fib_trie.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2175,6 +2175,12 @@ int fib_table_dump(struct fib_table *tb,
int count = cb->args[2];
t_key key = cb->args[3];

+ /* First time here, count and key are both always 0. Count > 0
+ * and key == 0 means the dump has wrapped around and we are done.
+ */
+ if (count && !key)
+ return skb->len;
while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
int err;

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