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fix lldpad netlink heap access overrun #122

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fix lldpad netlink heap access overrun #122

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24 changes: 18 additions & 6 deletions lldp_util.c
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Original file line number Diff line number Diff line change
Expand Up @@ -672,8 +672,9 @@ static struct nla_policy ifla_info_policy[IFLA_INFO_MAX + 1] =

int is_macvtap(const char *ifname)
{
int ret, s;
int ret, s, realsize;
struct nlmsghdr *nlh;
void *temp;
struct ifinfomsg *ifinfo;
struct nlattr *tb[IFLA_MAX+1],
*tb2[IFLA_INFO_MAX+1];
Expand All @@ -684,14 +685,12 @@ int is_macvtap(const char *ifname)
return false;
}

nlh = malloc(NLMSG_SIZE);
nlh = calloc(1, NLMSG_SIZE);

if (!nlh) {
goto out;
}

memset(nlh, 0, NLMSG_SIZE);

nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
nlh->nlmsg_type = RTM_GETLINK;
nlh->nlmsg_flags = NLM_F_REQUEST;
Expand All @@ -706,10 +705,23 @@ int is_macvtap(const char *ifname)
goto out_free;
}

memset(nlh, 0, NLMSG_SIZE);
do {
realsize = recv(s, NULL, 0, MSG_DONTWAIT | MSG_PEEK | MSG_TRUNC);
} while ((realsize < 0) && errno == EINTR);

if (realsize < 0) {
goto out_free;
}

temp = realloc(nlh, realsize);
if (!temp) {
goto out_free;
}
memset(temp, 0, realsize);
nlh = temp;

do {
ret = recv(s, (void *) nlh, NLMSG_SIZE, MSG_DONTWAIT);
ret = recv(s, (void *) nlh, realsize, MSG_DONTWAIT);
} while ((ret < 0) && errno == EINTR);

if (nlmsg_parse(nlh, sizeof(struct ifinfomsg),
Expand Down