Commit 52025ebaa29f for kernel

commit 52025ebaa29f4eb4ed8bf92ce83a68f24ab7fdf7
Author: Weiming Shi <bestswngs@gmail.com>
Date:   Wed Mar 25 14:10:58 2026 +0100

    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: df6fb868d611 ("[NETFILTER]: nfnetlink: convert to generic netlink attribute functions")
    Reported-by: Xiang Mei <xmei5@asu.edu>
    Signed-off-by: Weiming Shi <bestswngs@gmail.com>
    Signed-off-by: Florian Westphal <fw@strlen.de>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index b35a90955e2e..fcbe54940b2e 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -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();
 	}