linux-kernel - [PATCH] getdelays: Fix netlink attribute length

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Message-Id: <20200327173111.63922-1-dsahern@kernel.org>
Date:   Fri, 27 Mar 2020 11:31:11 -0600
From:   David Ahern <dsahern@...nel.org>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, David Ahern <dsahern@...nel.org>,
        Yafang Shao <laoar.shao@...il.com>,
        Johannes Berg <johannes@...solutions.net>,
        Shailabh Nagar <nagar@...son.ibm.com>
Subject: [PATCH] getdelays: Fix netlink attribute length

A recent change to the netlink code:
  6e237d099fac ("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: 9e06d3f9f6b1 ("per task delay accounting taskstats interface: documentation fix")
Signed-off-by: David Ahern <dsahern@...nel.org>
Tested-by: Yafang Shao <laoar.shao@...il.com>
Cc: Johannes Berg <johannes@...solutions.net>
Cc: Shailabh Nagar <nagar@...son.ibm.com>
---
 tools/accounting/getdelays.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/accounting/getdelays.c b/tools/accounting/getdelays.c
index 8cb504d30384..5ef1c15e88ad 100644
--- a/tools/accounting/getdelays.c
+++ b/tools/accounting/getdelays.c
@@ -136,7 +136,7 @@ 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);
 
-- 
2.17.1