diff mbox series

bpf: Fix out-of-bounds write in trie_get_next_key()

Message ID ZxcDzT/iv/f0Gyz0@localhost.localdomain (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series bpf: Fix out-of-bounds write in trie_get_next_key() | expand

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Commit Message

Byeonguk Jeong Oct. 22, 2024, 1:45 a.m. UTC 
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@gmail.com>
---
 kernel/bpf/lpm_trie.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Toke Høiland-Jørgensen Oct. 22, 2024, 9:43 a.m. UTC | #1 
Byeonguk Jeong <jungbu2855@gmail.com> writes:

> 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@gmail.com>

Makes sense!

Reviewed-by: Toke Høiland-Jørgensen <toke@kernel.org>
Alexei Starovoitov Oct. 22, 2024, 7:51 p.m. UTC | #2 
On Mon, Oct 21, 2024 at 6:49 PM Byeonguk Jeong <jungbu2855@gmail.com> wrote:
>
> 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.

Hmm. It sounds possible, but pls demonstrate it with a selftest.
With the amount of fuzzing I'm surprised it was not discovered earlier.

pw-bot: cr
diff mbox series

Patch

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)