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netfilter: nft_fib: reject fib expression on the netdev egress hook

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A fib expression in a netdev egress base chain dereferences nft_in(pkt),
NULL on the transmit path, causing a NULL pointer dereference at eval.
nft_fib_validate() masks the hook with NF_INET_* values, but netdev hook
numbers are a separate enum that aliases them (NF_NETDEV_EGRESS ==
NF_INET_LOCAL_IN), so an egress chain passes validation and then faults.

Add nft_fib_netdev_validate() that limits each result/flag to the netdev
hook where the device it reads exists: the input-device cases (OIF,
OIFNAME, ADDRTYPE with F_IIF) to ingress, the output-device case (ADDRTYPE
with F_OIF) to egress, ADDRTYPE with no device flag to both. Also restrict
nft_fib_validate() to NFPROTO_IPV4/IPV6/INET so its NF_INET_* masks are
not applied to another family's hooks.

Fixes: 42df6e1d22 ("netfilter: Introduce egress hook")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/netfilter-devel/ajxsjcDOnwllMfoR@strlen.de/
Signed-off-by: Theodor Arsenij Larionov-Trichkine <theodorlarionov@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
Theodor Arsenij Larionov-Trichkine
2026-06-29 12:53:11 +02:00
committed by Florian Westphal
parent bf5355cfde
commit d07955dd34
2 changed files with 37 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
net/netfilter/nft_fib.c
View File

@@ -31,6 +31,15 @@ int nft_fib_validate(const struct nft_ctx *ctx, const struct nft_expr *expr)
const struct nft_fib *priv = nft_expr_priv(expr);
unsigned int hooks;
switch (ctx->family) {
case NFPROTO_IPV4:
case NFPROTO_IPV6:
case NFPROTO_INET:
break;
default:
return -EOPNOTSUPP;
}
switch (priv->result) {
case NFT_FIB_RESULT_OIF:
case NFT_FIB_RESULT_OIFNAME:

29
net/netfilter/nft_fib_netdev.c
View File

@@ -50,6 +50,33 @@ static void nft_fib_netdev_eval(const struct nft_expr *expr,
regs->verdict.code = NFT_BREAK;
}
static int nft_fib_netdev_validate(const struct nft_ctx *ctx,
const struct nft_expr *expr)
{
const struct nft_fib *priv = nft_expr_priv(expr);
unsigned int hooks;
switch (priv->result) {
case NFT_FIB_RESULT_OIF:
case NFT_FIB_RESULT_OIFNAME:
hooks = (1 << NF_NETDEV_INGRESS);
break;
case NFT_FIB_RESULT_ADDRTYPE:
if (priv->flags & NFTA_FIB_F_IIF)
hooks = (1 << NF_NETDEV_INGRESS);
else if (priv->flags & NFTA_FIB_F_OIF)
hooks = (1 << NF_NETDEV_EGRESS);
else
hooks = (1 << NF_NETDEV_INGRESS) |
(1 << NF_NETDEV_EGRESS);
break;
default:
return -EINVAL;
}
return nft_chain_validate_hooks(ctx->chain, hooks);
}
static struct nft_expr_type nft_fib_netdev_type;
static const struct nft_expr_ops nft_fib_netdev_ops = {
.type = &nft_fib_netdev_type,
@@ -57,7 +84,7 @@ static const struct nft_expr_ops nft_fib_netdev_ops = {
.eval = nft_fib_netdev_eval,
.init = nft_fib_init,
.dump = nft_fib_dump,
.validate = nft_fib_validate,
.validate = nft_fib_netdev_validate,
};
static struct nft_expr_type nft_fib_netdev_type __read_mostly = {