diff options
| author | Florian Westphal <fw@strlen.de> | 2020-08-20 21:05:50 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-09-09 19:04:25 +0200 |
| commit | 86c459915577b0c87287b11f4dde44f908885461 (patch) | |
| tree | 873eeaccfc37a03a7d3356123a88ef60f55fce59 /net/netfilter | |
| parent | 3f21d1dd7cafb0230dc141e64ec5da622b3b1c46 (diff) | |
netfilter: nf_tables: fix destination register zeroing
[ Upstream commit 1e105e6afa6c3d32bfb52c00ffa393894a525c27 ]
Following bug was reported via irc:
nft list ruleset
set knock_candidates_ipv4 {
type ipv4_addr . inet_service
size 65535
elements = { 127.0.0.1 . 123,
127.0.0.1 . 123 }
}
..
udp dport 123 add @knock_candidates_ipv4 { ip saddr . 123 }
udp dport 123 add @knock_candidates_ipv4 { ip saddr . udp dport }
It should not have been possible to add a duplicate set entry.
After some debugging it turned out that the problem is the immediate
value (123) in the second-to-last rule.
Concatenations use 32bit registers, i.e. the elements are 8 bytes each,
not 6 and it turns out the kernel inserted
inet firewall @knock_candidates_ipv4
element 0100007f ffff7b00 : 0 [end]
element 0100007f 00007b00 : 0 [end]
Note the non-zero upper bits of the first element. It turns out that
nft_immediate doesn't zero the destination register, but this is needed
when the length isn't a multiple of 4.
Furthermore, the zeroing in nft_payload is broken. We can't use
[len / 4] = 0 -- if len is a multiple of 4, index is off by one.
Skip zeroing in this case and use a conditional instead of (len -1) / 4.
Fixes: 49499c3e6e18 ("netfilter: nf_tables: switch registers to 32 bit addressing")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'net/netfilter')
| -rw-r--r-- | net/netfilter/nft_payload.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c index 19446a89a2a8..b1a9f330a51f 100644 --- a/net/netfilter/nft_payload.c +++ b/net/netfilter/nft_payload.c @@ -79,7 +79,9 @@ static void nft_payload_eval(const struct nft_expr *expr, u32 *dest = ®s->data[priv->dreg]; int offset; - dest[priv->len / NFT_REG32_SIZE] = 0; + if (priv->len % NFT_REG32_SIZE) + dest[priv->len / NFT_REG32_SIZE] = 0; + switch (priv->base) { case NFT_PAYLOAD_LL_HEADER: if (!skb_mac_header_was_set(skb)) |