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android: fix blocking recvmsg due to netlink bug

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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 <info@bnoordhuis.nl>
This commit is contained in:
Jacob Segal 2017-08-02 11:13:28 -07:00 committed by Ben Noordhuis
parent 04adefafdf
commit 095e07cd79
1 changed files with 24 additions and 17 deletions
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41
src/unix/android-ifaddrs.c
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@ -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;
}