tools/accounting/getdelays.c: fix netlink attribute length

BugLink: https://bugs.launchpad.net/bugs/1874045

commit 4054ab64 upstream.

A recent change to the netlink code: 6e237d09 ("netlink: Relax attr
validation for fixed length types") logs a warning when programs send
messages with invalid attributes (e.g., wrong length for a u32).  Yafang
reported this error message for tools/accounting/getdelays.c.

send_cmd() is wrongly adding 1 to the attribute length.  As noted in
include/uapi/linux/netlink.h nla_len should be NLA_HDRLEN + payload
length, so drop the +1.

Fixes: 9e06d3f9 ("per task delay accounting taskstats interface: documentation fix")
Reported-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200327173111.63922-1-dsahern@kernel.orgSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

Documentation/accounting/getdelays.c

@@ -135,7 +135,7 @@ static int send_cmd(int sd, __u16 nlmsg_type, __u32 nlmsg_pid,
 	msg.g.version = 0x1;
 	na = (struct nlattr *) GENLMSG_DATA(&msg);
 	na->nla_type = nla_type;
-	na->nla_len = nla_len + 1 + NLA_HDRLEN;
+	na->nla_len = nla_len + NLA_HDRLEN;
 	memcpy(NLA_DATA(na), nla_data, nla_len);
 	msg.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);