From 387193faf4e8216ef201f2c685f69f6fa766ec46 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Sun, 18 Mar 2018 19:33:27 +0100 Subject: [PATCH] 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/libc-2.25.so) 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 (cherry picked from commit 37c876b55a2c00424ccda5a300ab5fdec1d88b22) --- src/attr.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/src/attr.c b/src/attr.c index 4f131874c11e4..0359ba959d7a0 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); }