From: Weiming Shi <redacted>
Since nft_set_commit_update() runs set commit callbacks before processing
NEWSETELEM transactions, nft_rbtree_gc_scan() can observe elements added by
the transaction being committed.
The scan records an interval end in rbe_end without checking the element's
transaction state. A later, unrelated expired start then moves both
elements to the expired list. The synchronous GC queue can free the new end
element before the transaction subsequently activates it, causing a
use-after-free.
Only consider elements that are fully active in both generations. This
keeps transaction-state elements out of the GC scan and preserves interval
pairing across skipped elements.
KASAN reports:
BUG: KASAN: slab-use-after-free in nft_setelem_activate
nft_setelem_activate net/netfilter/nf_tables_api.c:7047
nf_tables_commit net/netfilter/nf_tables_api.c:11137
Allocated by task 130:
nft_set_elem_init net/netfilter/nf_tables_api.c:6794
nft_add_set_elem net/netfilter/nf_tables_api.c:7523
Freed by task 130:
nft_trans_gc_trans_free net/netfilter/nf_tables_api.c:10506
rcu_core kernel/rcu/tree.c:2919
Fixes: 1e3b9e1c77fe ("netfilter: nf_tables: call set ops .commit when building new ruleset blob")
Reported-by: <redacted>
Assisted-by: LLM
Signed-off-by: Weiming Shi <redacted>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/netfilter/nft_set_rbtree.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
index 9894832281c4..12431b55752f 100644
--- a/net/netfilter/nft_set_rbtree.c
+++ b/net/netfilter/nft_set_rbtree.c
@@ -900,6 +900,8 @@ static void nft_rbtree_gc_scan(struct nft_set *set)
next = rb_next(node);
rbe = rb_entry(node, struct nft_rbtree_elem, node);
+ if (!nft_set_elem_active(&rbe->ext, NFT_GENMASK_ANY))
+ continue;
/* elements are reversed in the rbtree for historical reasons,
* from highest to lowest value, that is why end element is
--
2.47.3