From: Yehyeong Lee Date: Wed, 22 Jul 2026 12:28:17 +0000 (+0900) Subject: net: drop_monitor: fix info leak in NET_DM_ATTR_PAYLOAD X-Git-Url: http://git.ipfire.org/index.cgi?a=commitdiff_plain;h=5e9c8baee0329fbefe7c67aea945e2a07f15e98b;p=thirdparty%2Flinux.git net: drop_monitor: fix info leak in NET_DM_ATTR_PAYLOAD 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 --- diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index 2bf3cab5e557..b4d1ff2829b6 100644 --- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -671,9 +671,7 @@ 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; @@ -831,9 +829,7 @@ 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;