netlink: Fix nla_parse_nested_compat() to call nla_parse() directly

The purpose of nla_parse_nested_compat() is to parse attributes which
contain a struct followed by a stream of nested attributes.  So far,
it called nla_parse_nested() to parse the stream of nested attributes
which was wrong, as nla_parse_nested() expects a container attribute
as data which holds the attribute stream.  It needs to call
nla_parse() directly while pointing at the next possible alignment
point after the struct in the beginning of the attribute.

With this patch, I can no longer reproduce the reported leftover
warnings.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 5 deletions

diff --git a/include/net/netlink.h b/include/net/netlink.h
index a5506c42f03c..112dcdf7e34e 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -772,12 +772,13 @@ static inline int __nla_parse_nested_compat(struct nlattr *tb[], int maxtype,
                                             const struct nla_policy *policy,
                                             int len)
 {
-        if (nla_len(nla) < len)
+        int nested_len = nla_len(nla) - NLA_ALIGN(len);
+
+        if (nested_len < 0)
                 return -1;
-        if (nla_len(nla) >= NLA_ALIGN(len) + sizeof(struct nlattr))
-                return nla_parse_nested(tb, maxtype,
-                                        nla_data(nla) + NLA_ALIGN(len),
-                                        policy);
+        if (nested_len >= nla_attr_size(0))
+                return nla_parse(tb, maxtype, nla_data(nla) + NLA_ALIGN(len),
+                                 nested_len, policy);
         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
         return 0;
 }