netdev - [PATCH] net: rtnetlink: fix error handling in rtnl_fill

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Date:   Sat,  5 Mar 2022 10:13:46 -0800
From:   trix@...hat.com
To:     davem@...emloft.net, kuba@...nel.org, nathan@...nel.org,
        ndesaulniers@...gle.com, idosch@...dia.com, petrm@...dia.com,
        edumazet@...gle.com, avagin@...il.com, yajun.deng@...ux.dev,
        johannes.berg@...el.com, cong.wang@...edance.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Tom Rix <trix@...hat.com>
Subject: [PATCH] net: rtnetlink: fix error handling in rtnl_fill_statsinfo()

From: Tom Rix <trix@...hat.com>

The clang static analyzer reports this issue
rtnetlink.c:5481:2: warning: Undefined or garbage
  value returned to caller
  return err;
  ^~~~~~~~~~

There is a function level err variable, in the
list_for_each_entry_rcu block there is a shadow
err.  Remove the shadow.

In the same block, the call to nla_nest_start_noflag()
can fail without setting an err.  Set the err
to -EMSGSIZE.

Fixes: 216e690631f5 ("net: rtnetlink: rtnl_fill_statsinfo(): Permit non-EMSGSIZE error returns")
Signed-off-by: Tom Rix <trix@...hat.com>
---
 net/core/rtnetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a66b6761b88b1..a759f9e0a8476 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -5440,12 +5440,12 @@ static int rtnl_fill_statsinfo(struct sk_buff *skb, struct net_device *dev,
 		list_for_each_entry_rcu(af_ops, &rtnl_af_ops, list) {
 			if (af_ops->fill_stats_af) {
 				struct nlattr *af;
-				int err;
 
 				af = nla_nest_start_noflag(skb,
 							   af_ops->family);
 				if (!af) {
 					rcu_read_unlock();
+					err = -EMSGSIZE;
 					goto nla_put_failure;
 				}
 				err = af_ops->fill_stats_af(skb, dev);
-- 
2.26.3