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authorFlorian Westphal <fw@strlen.de>2020-08-20 21:05:50 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-09-12 11:45:27 +0200
commitf2695e268d974769856b3eaa1d8344b8e86e843f (patch)
tree813008505015beaca8568d3f172cb847484be913 /net
parent7d62ef1eadbaec8c60e3563a962429bb4c001cb0 (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')
-rw-r--r--net/netfilter/nft_payload.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 09b4b07eb676..ab3e7b14de09 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -74,7 +74,9 @@ static void nft_payload_eval(const struct nft_expr *expr,
u32 *dest = &regs->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))