Commit 52025eba authored by Weiming Shi's avatar Weiming Shi Committed by Pablo Neira Ayuso
Browse files

netfilter: nfnetlink_log: fix uninitialized padding leak in NFULA_PAYLOAD 



__build_packet_message() manually constructs the NFULA_PAYLOAD netlink
attribute using skb_put() and skb_copy_bits(), bypassing the standard
nla_reserve()/nla_put() helpers. While nla_total_size(data_len) bytes
are allocated (including NLA alignment padding), only data_len bytes
of actual packet data are copied. The trailing nla_padlen(data_len)
bytes (1-3 when data_len is not 4-byte aligned) are never initialized,
leaking stale heap contents to userspace via the NFLOG netlink socket.

Replace the manual attribute construction with nla_reserve(), which
handles the tailroom check, header setup, and padding zeroing via
__nla_reserve(). The subsequent skb_copy_bits() fills in the payload
data on top of the properly initialized attribute.

Fixes: df6fb868 ("[NETFILTER]: nfnetlink: convert to generic netlink attribute functions")
Reported-by: default avatarXiang Mei <xmei5@asu.edu>
Signed-off-by: default avatarWeiming Shi <bestswngs@gmail.com>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 6caefcd9

net/netfilter/nfnetlink_log.c

+2 −6
Original line number Diff line number Diff line
@@ -647,15 +647,11 @@ __build_packet_message(struct nfnl_log_net *log, 


	if (data_len) {

		struct nlattr *nla;

		int size = nla_attr_size(data_len);



		if (skb_tailroom(inst->skb) < nla_total_size(data_len))

		nla = nla_reserve(inst->skb, NFULA_PAYLOAD, data_len);

		if (!nla)

			goto nla_put_failure;



		nla = skb_put(inst->skb, nla_total_size(data_len));

		nla->nla_type = NFULA_PAYLOAD;

		nla->nla_len = size;



		if (skb_copy_bits(skb, 0, nla_data(nla), data_len))

			BUG();

	}