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Subject[PATCH v2 1/1] netfilter: nf_tables: fib: Drop IPV6 packages if IPv6 is disabled on boot
Date
If IPv6 is disabled on boot (ipv6.disable=1), but nft_fib_inet ends up
dealing with a IPv6 package, it causes a kernel panic in
fib6_node_lookup_1(), crashing in bad_page_fault.

The panic is caused by trying to deference a very low address (0x38
in ppc64le), due to ipv6.fib6_main_tbl = NULL.
BUG: Kernel NULL pointer dereference at 0x00000038

Fix this behavior by dropping IPv6 packages if !ipv6_mod_enabled().

Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
---
Changes from v1:
- Move drop logic from nft_fib_inet_eval() to nft_fib6_eval{,_type}
so it can affect other usages of these functions.

net/ipv6/netfilter/nft_fib_ipv6.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
index 7ece86afd079..75acc417e2ff 100644
--- a/net/ipv6/netfilter/nft_fib_ipv6.c
+++ b/net/ipv6/netfilter/nft_fib_ipv6.c
@@ -125,6 +125,11 @@ void nft_fib6_eval_type(const struct nft_expr *expr, struct nft_regs *regs,
u32 *dest = &regs->data[priv->dreg];
struct ipv6hdr *iph, _iph;

+ if (!ipv6_mod_enabled()) {
+ regs->verdict.code = NF_DROP;
+ return;
+ }
+
iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
if (!iph) {
regs->verdict.code = NFT_BREAK;
@@ -150,6 +155,11 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,
struct rt6_info *rt;
int lookup_flags;

+ if (!ipv6_mod_enabled()) {
+ regs->verdict.code = NF_DROP;
+ return;
+ }
+
if (priv->flags & NFTA_FIB_F_IIF)
oif = nft_in(pkt);
else if (priv->flags & NFTA_FIB_F_OIF)
--
2.20.1
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