libnetlink: Fix extack attribute parsing

Initialize tb in nl_dump_ext_err since not all attributes will be
sent in the messages.

Add error checking on mnl_attr_parse and print messages on the off
chance the ext ack attributes fail to validate.

Signed-off-by: David Ahern <dsahern@gmail.com>

diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 81a344abff27a6f65d59a6c229741cf1b8344171..874e660be7eb4e028d240e250f959ab1d66fe98d 100644 (file)
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -49,13 +49,17 @@ static int err_attr_cb(const struct nlattr *attr, void *data)
        const struct nlattr **tb = data;
        uint16_t type;
 
-       if (mnl_attr_type_valid(attr, NLMSGERR_ATTR_MAX) < 0)
+       if (mnl_attr_type_valid(attr, NLMSGERR_ATTR_MAX) < 0) {
+               fprintf(stderr, "Invalid extack attribute\n");
                return MNL_CB_ERROR;
+       }
 
        type = mnl_attr_get_type(attr);
-       if (mnl_attr_validate(attr, extack_policy[type]) < 0)
+       if (mnl_attr_validate(attr, extack_policy[type]) < 0) {
+               fprintf(stderr, "extack attribute %d failed validation\n",
+                       type);
                return MNL_CB_ERROR;
-
+       }
 
        tb[type] = attr;
        return MNL_CB_OK;
@@ -64,7 +68,7 @@ static int err_attr_cb(const struct nlattr *attr, void *data)
 /* dump netlink extended ack error message */
 static int nl_dump_ext_err(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn)
 {
-       struct nlattr *tb[NLMSGERR_ATTR_MAX + 1];
+       struct nlattr *tb[NLMSGERR_ATTR_MAX + 1] = {};
        const struct nlmsgerr *err = mnl_nlmsg_get_payload(nlh);
        const struct nlmsghdr *err_nlh = NULL;
        unsigned int hlen = sizeof(*err);
@@ -79,7 +83,8 @@ static int nl_dump_ext_err(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn)
        if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
                hlen += mnl_nlmsg_get_payload_len(&err->msg);
 
-       mnl_attr_parse(nlh, hlen, err_attr_cb, tb);
+       if (mnl_attr_parse(nlh, hlen, err_attr_cb, tb) != MNL_CB_OK)
+               return 0;
 
        if (tb[NLMSGERR_ATTR_MSG])
                errmsg = mnl_attr_get_str(tb[NLMSGERR_ATTR_MSG]);