nf_osf_ttl() calls __in_dev_get_rcu(skb->dev) and passes the result
to in_dev_for_each_ifa_rcu() without checking for NULL. When the
receiving device has no IPv4 configuration (ip_ptr is NULL),
__in_dev_get_rcu() returns NULL and in_dev_for_each_ifa_rcu()
dereferences it unconditionally, causing a kernel crash.
This can happen when a packet arrives on a device that has had its
IPv4 configuration removed (e.g., MTU set below IPV4_MIN_MTU causing
inetdev_destroy) or on a device that was never assigned an IPv4
address, while an xt_osf or nft_osf rule with TTL_LESS mode is
active and the packet TTL exceeds the fingerprint TTL.
Add a NULL check for in_dev before the iteration. When in_dev is
NULL, return 0 (no match) since source-address locality cannot be
determined without IPv4 addresses on the device.
KASAN: null-ptr-deref in range
[0x0000000000000010-0x0000000000000017]
RIP: 0010:nf_osf_match_one+0x204/0xa70
Call Trace:
nf_osf_match+0x2f8/0x780
xt_osf_match_packet+0x11c/0x1f0
ipt_do_table+0x7fe/0x12b0
nf_hook_slow+0xac/0x1e0
ip_rcv+0x123/0x370
__netif_receive_skb_one_core+0x166/0x1b0
process_backlog+0x197/0x590
__napi_poll+0xa1/0x540
net_rx_action+0x401/0xd80
handle_softirqs+0x19f/0x610
Fixes: a218dc82f0b5 ("netfilter: nft_osf: Add ttl option support")
Signed-off-by: Kito Xu (veritas501)
---
net/netfilter/nfnetlink_osf.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
index d64ce21c7b55..85dbd47dbbd4 100644
--- a/net/netfilter/nfnetlink_osf.c
+++ b/net/netfilter/nfnetlink_osf.c
@@ -43,6 +43,9 @@ static inline int nf_osf_ttl(const struct sk_buff *skb,
else if (ip->ttl <= f_ttl)
return 1;
+ if (!in_dev)
+ return 0;
+
in_dev_for_each_ifa_rcu(ifa, in_dev) {
if (inet_ifa_match(ip->saddr, ifa)) {
ret = (ip->ttl == f_ttl);
--
2.43.0