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netfilter: nf_queue: do not allow packet truncation below transport header offset

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Domingo Dirutigliano and Nicola Guerrera report kernel panic when
sending nf_queue verdict with 1-byte nfta_payload attribute.

The IP/IPv6 stack pulls the IP(v6) header from the packet after the
input hook.

If user truncates the packet below the header size, this skb_pull() will
result in a malformed skb (skb->len < 0).

Fixes: 7af4cc3fa1 ("[NETFILTER]: Add "nfnetlink_queue" netfilter queue handler over nfnetlink")
Reported-by: Domingo Dirutigliano <pwnzer0tt1@proton.me>
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2022-07-26 12:42:06 +02:00
parent 9b134b1694
commit 99a63d36cb
1 changed files with 6 additions and 1 deletions
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7
net/netfilter/nfnetlink_queue.c
View file

@ -843,11 +843,16 @@ nfqnl_enqueue_packet(struct nf_queue_entry *entry, unsigned int queuenum)
}
static int
nfqnl_mangle(void *data, int data_len, struct nf_queue_entry *e, int diff)
nfqnl_mangle(void *data, unsigned int data_len, struct nf_queue_entry *e, int diff)
{
struct sk_buff *nskb;
if (diff < 0) {
unsigned int min_len = skb_transport_offset(e->skb);
if (data_len < min_len)
return -EINVAL;
if (pskb_trim(e->skb, data_len))
return -ENOMEM;
} else if (diff > 0) {