6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yehyeong Lee [ Upstream commit 5e9c8baee0329fbefe7c67aea945e2a07f15e98b ] net_dm_packet_report_fill() and net_dm_hw_packet_report_fill() open code the NET_DM_ATTR_PAYLOAD attribute to avoid zeroing the packet payload before overwriting it with skb_copy_bits(). skb_put() reserves nla_total_size(payload_len), i.e. the header plus the NLA_ALIGN() padding, but only payload_len bytes are copied in. When payload_len is not a multiple of 4 the 1-3 padding bytes are never initialized and are leaked to user space inside the netlink message. KMSAN confirms the leak for the software path when the packet payload length is not 4-byte aligned: BUG: KMSAN: kernel-infoleak in _copy_to_iter _copy_to_iter __skb_datagram_iter skb_copy_datagram_iter netlink_recvmsg sock_recvmsg __sys_recvfrom Uninit was created at: kmem_cache_alloc_node_noprof __alloc_skb net_dm_packet_work Bytes 173-175 of 176 are uninitialized Use __nla_reserve(), which sets up the attribute header and zeroes the padding, instead of open coding the attribute construction. Fixes: ca30707dee2b ("drop_monitor: Add packet alert mode") Fixes: 5e58109b1ea4 ("drop_monitor: Add support for packet alert mode for hardware drops") Suggested-by: Eric Dumazet Signed-off-by: Yehyeong Lee Link: https://patch.msgid.link/20260722122817.5548-1-yhlee@isslab.korea.ac.kr Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/core/drop_monitor.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index fe560b2d161f9..60ca18b440a34 100644 --- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -669,9 +669,7 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb, if (nla_put_u16(msg, NET_DM_ATTR_PROTO, be16_to_cpu(skb->protocol))) goto nla_put_failure; - attr = skb_put(msg, nla_total_size(payload_len)); - attr->nla_type = NET_DM_ATTR_PAYLOAD; - attr->nla_len = nla_attr_size(payload_len); + attr = __nla_reserve(msg, NET_DM_ATTR_PAYLOAD, payload_len); if (skb_copy_bits(skb, 0, nla_data(attr), payload_len)) goto nla_put_failure; @@ -829,9 +827,7 @@ static int net_dm_hw_packet_report_fill(struct sk_buff *msg, if (nla_put_u16(msg, NET_DM_ATTR_PROTO, be16_to_cpu(skb->protocol))) goto nla_put_failure; - attr = skb_put(msg, nla_total_size(payload_len)); - attr->nla_type = NET_DM_ATTR_PAYLOAD; - attr->nla_len = nla_attr_size(payload_len); + attr = __nla_reserve(msg, NET_DM_ATTR_PAYLOAD, payload_len); if (skb_copy_bits(skb, 0, nla_data(attr), payload_len)) goto nla_put_failure; -- 2.53.0