linux-kernel - [PATCH v2 bpf 1/2] bpf: Fix out-of-bounds write in trie_get_next

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Message-ID: <Zxx384ZfdlFYnz6J@localhost.localdomain>
Date: Sat, 26 Oct 2024 14:02:43 +0900
From: Byeonguk Jeong <jungbu2855@...il.com>
To: Toke Høiland-Jørgensen <toke@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Hou Tao <houtao@...weicloud.com>,
	Yonghong Song <yonghong.song@...ux.dev>
Cc: linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH v2 bpf 1/2] bpf: Fix out-of-bounds write in
 trie_get_next_key()

trie_get_next_key() allocates a node stack with size trie->max_prefixlen,
while it writes (trie->max_prefixlen + 1) nodes to the stack when it has
full paths from the root to leaves. For example, consider a trie with
max_prefixlen is 8, and the nodes with key 0x00/0, 0x00/1, 0x00/2, ...
0x00/8 inserted. Subsequent calls to trie_get_next_key with _key with
.prefixlen = 8 make 9 nodes be written on the node stack with size 8.

Fixes: b471f2f1de8b ("bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE map")
Signed-off-by: Byeonguk Jeong <jungbu2855@...il.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@...nel.org>
Tested-by: Hou Tao <houtao1@...wei.com>
---
v1 -> v2: nothing changed
---
 kernel/bpf/lpm_trie.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index 0218a5132ab5..9b60eda0f727 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -655,7 +655,7 @@ static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key)
 	if (!key || key->prefixlen > trie->max_prefixlen)
 		goto find_leftmost;
 
-	node_stack = kmalloc_array(trie->max_prefixlen,
+	node_stack = kmalloc_array(trie->max_prefixlen + 1,
 				   sizeof(struct lpm_trie_node *),
 				   GFP_ATOMIC | __GFP_NOWARN);
 	if (!node_stack)
-- 
2.43.5