diff options
authorFlorian Westphal <>2018-03-18 19:33:27 +0100
committerFlorian Westphal <>2018-03-20 13:22:40 +0100
commit37c876b55a2c00424ccda5a300ab5fdec1d88b22 (patch)
parent577ad36084ffc76dadb98bf580b9811ff45ad79d (diff)
libmnl: zero attribute padding
Sergei Trofimovich reports 'uninitialized bytes' warnings from nftables: Syscall param sendmsg(msg.msg_iov[0]) points to uninitialised byte(s) at 0x55B9EFB: sendmsg (in /lib64/ by 0x43E658: mnl_nft_socket_sendmsg (mnl.c:239) by 0x43E658: mnl_batch_talk (mnl.c:254) by 0x407898: nft_netlink (libnftables.c:58) by 0x407898: nft_run (libnftables.c:96) by 0x407CD5: nft_run_cmd_from_buffer (libnftables.c:291) by 0x406EDE: main (main.c:274) This is harmless, the uninitialized memory is the padding that sometimes needs to be inserted between end of an attribute and the beginning of the new attribute. Zero it to silence memory sanitizer output. Signed-off-by: Florian Westphal <> Acked-by: Pablo Neira Ayuso <>
1 files changed, 5 insertions, 0 deletions
diff --git a/src/attr.c b/src/attr.c
index 4f13187..0359ba9 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -412,10 +412,15 @@ void mnl_attr_put(struct nlmsghdr *nlh, uint16_t type, size_t len,
struct nlattr *attr = mnl_nlmsg_get_payload_tail(nlh);
uint16_t payload_len = MNL_ALIGN(sizeof(struct nlattr)) + len;
+ int pad;
attr->nla_type = type;
attr->nla_len = payload_len;
memcpy(mnl_attr_get_payload(attr), data, len);
+ pad = MNL_ALIGN(len) - len;
+ if (pad > 0)
+ memset(mnl_attr_get_payload(attr) + len, 0, pad);
nlh->nlmsg_len += MNL_ALIGN(payload_len);