From 095e07cd79e6810fc35983e5c7532300b3bb4d4e Mon Sep 17 00:00:00 2001 From: Jacob Segal Date: Wed, 2 Aug 2017 11:13:28 -0700 Subject: [PATCH] android: fix blocking recvmsg due to netlink bug Code was assuming that the nl_pid was always equal to the process id. As the netlink documentation says, "nl_pid is usually the PID of the process owning the destination socket. However, nl_pid identifies a netlink socket, not a process". There are two cases in which this assumption breaks down. The first is that some other part of the application has already bound a netlink socket with a nl_pid equal to the PID of the process. The second is Android version 5.0 where it appears that nl_pid is not always defaulted to the PID of the process. The result of this bad assumption is that netlink message responses to our request are ignored due to having a bad nl_pid. We eventually run out of messages on the netlink socket and block forever awaiting our response. PR-URL: https://github.com/libuv/libuv/pull/1451 Reviewed-By: Ben Noordhuis --- src/unix/android-ifaddrs.c | 41 ++++++++++++++++++++++---------------- 1 file changed, 24 insertions(+), 17 deletions(-) diff --git a/src/unix/android-ifaddrs.c b/src/unix/android-ifaddrs.c index 30f681b7..1a842ced 100644 --- a/src/unix/android-ifaddrs.c +++ b/src/unix/android-ifaddrs.c @@ -43,9 +43,10 @@ typedef struct NetlinkList unsigned int m_size; } NetlinkList; -static int netlink_socket(void) +static int netlink_socket(pid_t *p_pid) { struct sockaddr_nl l_addr; + socklen_t l_len; int l_socket = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE); if(l_socket < 0) @@ -61,6 +62,14 @@ static int netlink_socket(void) return -1; } + l_len = sizeof(l_addr); + if(getsockname(l_socket, (struct sockaddr *)&l_addr, &l_len) < 0) + { + close(l_socket); + return -1; + } + *p_pid = l_addr.nl_pid; + return l_socket; } @@ -128,7 +137,7 @@ static int netlink_recv(int p_socket, void *p_buffer, size_t p_len) } } -static struct nlmsghdr *getNetlinkResponse(int p_socket, int *p_size, int *p_done) +static struct nlmsghdr *getNetlinkResponse(int p_socket, pid_t p_pid, int *p_size, int *p_done) { size_t l_size = 4096; void *l_buffer = NULL; @@ -153,11 +162,10 @@ static struct nlmsghdr *getNetlinkResponse(int p_socket, int *p_size, int *p_don } if(l_read >= 0) { - pid_t l_pid = getpid(); struct nlmsghdr *l_hdr; for(l_hdr = (struct nlmsghdr *)l_buffer; NLMSG_OK(l_hdr, (unsigned int)l_read); l_hdr = (struct nlmsghdr *)NLMSG_NEXT(l_hdr, l_read)) { - if((pid_t)l_hdr->nlmsg_pid != l_pid || (int)l_hdr->nlmsg_seq != p_socket) + if((pid_t)l_hdr->nlmsg_pid != p_pid || (int)l_hdr->nlmsg_seq != p_socket) { continue; } @@ -207,7 +215,7 @@ static void freeResultList(NetlinkList *p_list) } } -static NetlinkList *getResultList(int p_socket, int p_request) +static NetlinkList *getResultList(int p_socket, int p_request, pid_t p_pid) { int l_size; int l_done; @@ -227,7 +235,7 @@ static NetlinkList *getResultList(int p_socket, int p_request) { NetlinkList *l_item; - struct nlmsghdr *l_hdr = getNetlinkResponse(p_socket, &l_size, &l_done); + struct nlmsghdr *l_hdr = getNetlinkResponse(p_socket, p_pid, &l_size, &l_done); /* Error */ if(!l_hdr) { @@ -578,18 +586,17 @@ static int interpretAddr(struct nlmsghdr *p_hdr, struct ifaddrs **p_resultList, return 0; } -static int interpretLinks(int p_socket, NetlinkList *p_netlinkList, struct ifaddrs **p_resultList) +static int interpretLinks(int p_socket, pid_t p_pid, NetlinkList *p_netlinkList, struct ifaddrs **p_resultList) { int l_numLinks = 0; - pid_t l_pid = getpid(); for(; p_netlinkList; p_netlinkList = p_netlinkList->m_next) { unsigned int l_nlsize = p_netlinkList->m_size; struct nlmsghdr *l_hdr; for(l_hdr = p_netlinkList->m_data; NLMSG_OK(l_hdr, l_nlsize); l_hdr = NLMSG_NEXT(l_hdr, l_nlsize)) { - if((pid_t)l_hdr->nlmsg_pid != l_pid || (int)l_hdr->nlmsg_seq != p_socket) + if((pid_t)l_hdr->nlmsg_pid != p_pid || (int)l_hdr->nlmsg_seq != p_socket) { continue; } @@ -612,16 +619,15 @@ static int interpretLinks(int p_socket, NetlinkList *p_netlinkList, struct ifadd return l_numLinks; } -static int interpretAddrs(int p_socket, NetlinkList *p_netlinkList, struct ifaddrs **p_resultList, int p_numLinks) +static int interpretAddrs(int p_socket, pid_t p_pid, NetlinkList *p_netlinkList, struct ifaddrs **p_resultList, int p_numLinks) { - pid_t l_pid = getpid(); for(; p_netlinkList; p_netlinkList = p_netlinkList->m_next) { unsigned int l_nlsize = p_netlinkList->m_size; struct nlmsghdr *l_hdr; for(l_hdr = p_netlinkList->m_data; NLMSG_OK(l_hdr, l_nlsize); l_hdr = NLMSG_NEXT(l_hdr, l_nlsize)) { - if((pid_t)l_hdr->nlmsg_pid != l_pid || (int)l_hdr->nlmsg_seq != p_socket) + if((pid_t)l_hdr->nlmsg_pid != p_pid || (int)l_hdr->nlmsg_seq != p_socket) { continue; } @@ -648,6 +654,7 @@ int getifaddrs(struct ifaddrs **ifap) int l_socket; int l_result; int l_numLinks; + pid_t l_pid; NetlinkList *l_linkResults; NetlinkList *l_addrResults; @@ -657,20 +664,20 @@ int getifaddrs(struct ifaddrs **ifap) } *ifap = NULL; - l_socket = netlink_socket(); + l_socket = netlink_socket(&l_pid); if(l_socket < 0) { return -1; } - l_linkResults = getResultList(l_socket, RTM_GETLINK); + l_linkResults = getResultList(l_socket, RTM_GETLINK, l_pid); if(!l_linkResults) { close(l_socket); return -1; } - l_addrResults = getResultList(l_socket, RTM_GETADDR); + l_addrResults = getResultList(l_socket, RTM_GETADDR, l_pid); if(!l_addrResults) { close(l_socket); @@ -679,8 +686,8 @@ int getifaddrs(struct ifaddrs **ifap) } l_result = 0; - l_numLinks = interpretLinks(l_socket, l_linkResults, ifap); - if(l_numLinks == -1 || interpretAddrs(l_socket, l_addrResults, ifap, l_numLinks) == -1) + l_numLinks = interpretLinks(l_socket, l_pid, l_linkResults, ifap); + if(l_numLinks == -1 || interpretAddrs(l_socket, l_pid, l_addrResults, ifap, l_numLinks) == -1) { l_result = -1; }