From: Liping Zhang <zlpnobody@xxxxxxxxx>
Packets may race when create the new element in nft_hash_update:
CPU0 CPU1
lookup_fast - fail lookup_fast - fail
new - ok new - ok
insert - ok insert - fail(EEXIST)
So when race happened, we reuse the existing element. Otherwise,
these *racing* packets will not be handled properly.
Signed-off-by: Liping Zhang <zlpnobody@xxxxxxxxx>
---
net/netfilter/nft_set_hash.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/net/netfilter/nft_set_hash.c b/net/netfilter/nft_set_hash.c
index 88d9fc8..a3dface 100644
--- a/net/netfilter/nft_set_hash.c
+++ b/net/netfilter/nft_set_hash.c
@@ -98,7 +98,7 @@ static bool nft_hash_update(struct nft_set *set, const u32 *key,
const struct nft_set_ext **ext)
{
struct nft_hash *priv = nft_set_priv(set);
- struct nft_hash_elem *he;
+ struct nft_hash_elem *he, *prev;
struct nft_hash_cmp_arg arg = {
.genmask = NFT_GENMASK_ANY,
.set = set,
@@ -112,9 +112,18 @@ static bool nft_hash_update(struct nft_set *set, const u32 *key,
he = new(set, expr, regs);
if (he == NULL)
goto err1;
- if (rhashtable_lookup_insert_key(&priv->ht, &arg, &he->node,
- nft_hash_params))
+
+ prev = rhashtable_lookup_get_insert_key(&priv->ht, &arg, &he->node,
+ nft_hash_params);
+ if (IS_ERR(prev))
goto err2;
+
+ /* Another cpu may race to insert the element with the same key */
+ if (prev) {
+ nft_set_elem_destroy(set, he, true);
+ he = prev;
+ }
+
out:
*ext = &he->ext;
return true;
--
2.5.5
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