[PATCH] getdelays: Fix netlink attribute length

[PATCH] getdelays: Fix netlink attribute length

[David Ahern]

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@kernel.org>
Tested-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Shailabh Nagar <nagar@watson.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

Re: [PATCH] getdelays: Fix netlink attribute length

[Andrew Morton]

On Fri, 27 Mar 2020 11:31:11 -0600 David Ahern <dsahern@kernel.org> wrote:

> 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.

Thanks.

> Fixes: 9e06d3f9f6b1 ("per task delay accounting taskstats interface: documentation fix")
> Signed-off-by: David Ahern <dsahern@kernel.org>
> Tested-by: Yafang Shao <laoar.shao@gmail.com>

I'll add Reported-by: as well.

> Cc: Johannes Berg <johannes@sipsolutions.net>
> Cc: Shailabh Nagar <nagar@watson.ibm.com>

Is this worth a cc:stable?

Re: [PATCH] getdelays: Fix netlink attribute length

[David Ahern]

On 3/28/20 2:03 PM, Andrew Morton wrote:
>> Cc: Johannes Berg <johannes@sipsolutions.net>
>> Cc: Shailabh Nagar <nagar@watson.ibm.com>
> 
> Is this worth a cc:stable?
> 
> 

sure.