From c41868152a95db5f759bb7da491615eca99e9a40 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 6 Nov 2018 15:13:20 +0000 Subject: [PATCH 1/4] slirp: Don't pass possibly -1 fd to send() Coverity complains (CID 1005726) that we might pass -1 as the fd argument to send() in slirp_send(), because we previously checked for "so->s == -1 && so->extra". The case of "so->s == -1 but so->extra NULL" should not in theory happen, but it is hard to guarantee because various places in the code do so->s = qemu_socket(...) and so will end up with so->s == -1 on failure, and not all the paths which call that always throw away the socket in that case (eg tcp_fconnect()). So just check specifically for the condition and fail slirp_send(). Signed-off-by: Peter Maydell Signed-off-by: Samuel Thibault --- slirp/slirp.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/slirp/slirp.c b/slirp/slirp.c index 51de41fc02..3c3c03b22f 100644 --- a/slirp/slirp.c +++ b/slirp/slirp.c @@ -1091,6 +1091,17 @@ ssize_t slirp_send(struct socket *so, const void *buf, size_t len, int flags) return len; } + if (so->s == -1) { + /* + * This should in theory not happen but it is hard to be + * sure because some code paths will end up with so->s == -1 + * on a failure but don't dispose of the struct socket. + * Check specifically, so we don't pass -1 to send(). + */ + errno = EBADF; + return -1; + } + return send(so->s, buf, len, flags); } From 84ec9bfaf239b61bac3e43f708772937401e0e63 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 6 Nov 2018 15:13:21 +0000 Subject: [PATCH 2/4] slirp: Use g_new() to allocate sockets in socreate() The slirp socreate() function can only fail if the attempt to malloc() the struct socket fails. Switch to using g_new() instead, which will allow us to remove the error-handling code from its callers. Signed-off-by: Peter Maydell Signed-off-by: Samuel Thibault --- slirp/socket.c | 14 ++++++-------- slirp/tcp_input.c | 4 ++-- slirp/tcp_subr.c | 2 +- 3 files changed, 9 insertions(+), 11 deletions(-) diff --git a/slirp/socket.c b/slirp/socket.c index 322383a1f9..35a9a14565 100644 --- a/slirp/socket.c +++ b/slirp/socket.c @@ -46,17 +46,15 @@ struct socket *solookup(struct socket **last, struct socket *head, struct socket * socreate(Slirp *slirp) { - struct socket *so; + struct socket *so = g_new(struct socket, 1); - so = (struct socket *)malloc(sizeof(struct socket)); - if(so) { memset(so, 0, sizeof(struct socket)); so->so_state = SS_NOFDREF; so->s = -1; so->slirp = slirp; so->pollfds_idx = -1; - } - return(so); + + return so; } /* @@ -110,7 +108,7 @@ sofree(struct socket *so) if (so->so_tcpcb) { free(so->so_tcpcb); } - free(so); + g_free(so); } size_t sopreprbuf(struct socket *so, struct iovec *iov, int *np) @@ -721,8 +719,8 @@ tcp_listen(Slirp *slirp, uint32_t haddr, u_int hport, uint32_t laddr, /* Don't tcp_attach... we don't need so_snd nor so_rcv */ if ((so->so_tcpcb = tcp_newtcpcb(so)) == NULL) { - free(so); - return NULL; + g_free(so); + return NULL; } insque(so, &slirp->tcb); diff --git a/slirp/tcp_input.c b/slirp/tcp_input.c index 07bcbdb2dd..4f79c95fdb 100644 --- a/slirp/tcp_input.c +++ b/slirp/tcp_input.c @@ -432,8 +432,8 @@ findso: if ((so = socreate(slirp)) == NULL) goto dropwithreset; if (tcp_attach(so) < 0) { - free(so); /* Not sofree (if it failed, it's not insqued) */ - goto dropwithreset; + g_free(so); /* Not sofree (if it failed, it's not insqued) */ + goto dropwithreset; } sbreserve(&so->so_snd, TCP_SNDSPACE); diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c index 8d0f94b75f..0270c89ae3 100644 --- a/slirp/tcp_subr.c +++ b/slirp/tcp_subr.c @@ -475,7 +475,7 @@ void tcp_connect(struct socket *inso) return; } if (tcp_attach(so) < 0) { - free(so); /* NOT sofree */ + g_free(so); /* NOT sofree */ return; } so->lhost = inso->lhost; From 4ded9bb54ceefeb68e766fe9aafc10de934c4501 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 6 Nov 2018 15:13:22 +0000 Subject: [PATCH 3/4] slirp: Remove code that handles socreate() failure Now that socreate() can never fail, we can remove the code that was trying to handle that situation. In particular this removes code in tcp_connect() that provoked Coverity to complain (CID 1005724): in closesocket(accept(inso->s, (struct sockaddr *)&addr, &addrlen)); if the accept() call fails then we pass closesocket() -1 instead of a valid file descriptor. Signed-off-by: Peter Maydell Signed-off-by: Samuel Thibault --- slirp/ip_icmp.c | 2 +- slirp/slirp.c | 3 --- slirp/socket.c | 3 --- slirp/tcp_input.c | 3 +-- slirp/tcp_subr.c | 5 ----- slirp/udp.c | 6 ------ slirp/udp6.c | 3 --- 7 files changed, 2 insertions(+), 23 deletions(-) diff --git a/slirp/ip_icmp.c b/slirp/ip_icmp.c index da100d1f55..9210eef3f3 100644 --- a/slirp/ip_icmp.c +++ b/slirp/ip_icmp.c @@ -160,7 +160,7 @@ icmp_input(struct mbuf *m, int hlen) } else { struct socket *so; struct sockaddr_storage addr; - if ((so = socreate(slirp)) == NULL) goto freeit; + so = socreate(slirp); if (icmp_send(so, m, hlen) == 0) { return; } diff --git a/slirp/slirp.c b/slirp/slirp.c index 3c3c03b22f..322edf51eb 100644 --- a/slirp/slirp.c +++ b/slirp/slirp.c @@ -1477,9 +1477,6 @@ static int slirp_state_load(QEMUFile *f, void *opaque, int version_id) int ret; struct socket *so = socreate(slirp); - if (!so) - return -ENOMEM; - ret = vmstate_load_state(f, &vmstate_slirp_socket, so, version_id); if (ret < 0) diff --git a/slirp/socket.c b/slirp/socket.c index 35a9a14565..c01d8696af 100644 --- a/slirp/socket.c +++ b/slirp/socket.c @@ -713,9 +713,6 @@ tcp_listen(Slirp *slirp, uint32_t haddr, u_int hport, uint32_t laddr, DEBUG_ARG("flags = %x", flags); so = socreate(slirp); - if (!so) { - return NULL; - } /* Don't tcp_attach... we don't need so_snd nor so_rcv */ if ((so->so_tcpcb = tcp_newtcpcb(so)) == NULL) { diff --git a/slirp/tcp_input.c b/slirp/tcp_input.c index 4f79c95fdb..d073ef9525 100644 --- a/slirp/tcp_input.c +++ b/slirp/tcp_input.c @@ -429,8 +429,7 @@ findso: if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN) goto dropwithreset; - if ((so = socreate(slirp)) == NULL) - goto dropwithreset; + so = socreate(slirp); if (tcp_attach(so) < 0) { g_free(so); /* Not sofree (if it failed, it's not insqued) */ goto dropwithreset; diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c index 0270c89ae3..fa61349cbb 100644 --- a/slirp/tcp_subr.c +++ b/slirp/tcp_subr.c @@ -469,11 +469,6 @@ void tcp_connect(struct socket *inso) so = inso; } else { so = socreate(slirp); - if (so == NULL) { - /* If it failed, get rid of the pending connection */ - closesocket(accept(inso->s, (struct sockaddr *)&addr, &addrlen)); - return; - } if (tcp_attach(so) < 0) { g_free(so); /* NOT sofree */ return; diff --git a/slirp/udp.c b/slirp/udp.c index e5bf065bf2..c47870a61b 100644 --- a/slirp/udp.c +++ b/slirp/udp.c @@ -171,9 +171,6 @@ udp_input(register struct mbuf *m, int iphlen) * create one */ so = socreate(slirp); - if (!so) { - goto bad; - } if (udp_attach(so, AF_INET) == -1) { DEBUG_MISC((dfd," udp_attach errno = %d-%s\n", errno,strerror(errno))); @@ -331,9 +328,6 @@ udp_listen(Slirp *slirp, uint32_t haddr, u_int hport, uint32_t laddr, socklen_t addrlen = sizeof(struct sockaddr_in); so = socreate(slirp); - if (!so) { - return NULL; - } so->s = qemu_socket(AF_INET,SOCK_DGRAM,0); if (so->s < 0) { sofree(so); diff --git a/slirp/udp6.c b/slirp/udp6.c index 7c4a6b003a..986010f0d3 100644 --- a/slirp/udp6.c +++ b/slirp/udp6.c @@ -91,9 +91,6 @@ void udp6_input(struct mbuf *m) if (so == NULL) { /* If there's no socket for this packet, create one. */ so = socreate(slirp); - if (!so) { - goto bad; - } if (udp_attach(so, AF_INET6) == -1) { DEBUG_MISC((dfd, " udp6_attach errno = %d-%s\n", errno, strerror(errno))); From 5c75f3adbbfcdf8fae6e74875b44efb8d928974a Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 6 Nov 2018 15:13:23 +0000 Subject: [PATCH 4/4] slirp: fork_exec(): create and connect child socket before fork() Currently fork_exec() fork()s, and then creates and connects the child socket which it uses for communication with the parent in the child process. This is awkward because the child has no mechanism to report failure back to the parent, which might end up blocked forever in accept(). The child code also has an issue pointed out by Coverity (CID 1005727), where if the qemu_socket() call fails it will pass -1 as a file descriptor to connect(). Fix these issues by moving the creation of the child's end of the socket to before the fork(), where we are in a position to handle a possible failure. Signed-off-by: Peter Maydell Signed-off-by: Samuel Thibault --- slirp/misc.c | 55 ++++++++++++++++++++++++++++++++-------------------- 1 file changed, 34 insertions(+), 21 deletions(-) diff --git a/slirp/misc.c b/slirp/misc.c index 260187b6b6..57bdd808e2 100644 --- a/slirp/misc.c +++ b/slirp/misc.c @@ -85,9 +85,10 @@ fork_exec(struct socket *so, const char *ex, int do_pty) int fork_exec(struct socket *so, const char *ex, int do_pty) { - int s; - struct sockaddr_in addr; + int s, cs; + struct sockaddr_in addr, csaddr; socklen_t addrlen = sizeof(addr); + socklen_t csaddrlen = sizeof(csaddr); int opt; const char *argv[256]; /* don't want to clobber the original */ @@ -120,10 +121,35 @@ fork_exec(struct socket *so, const char *ex, int do_pty) } } + if (getsockname(s, (struct sockaddr *)&csaddr, &csaddrlen) < 0) { + closesocket(s); + return 0; + } + cs = qemu_socket(AF_INET, SOCK_STREAM, 0); + if (cs < 0) { + closesocket(s); + return 0; + } + csaddr.sin_addr = loopback_addr; + /* + * This connect won't block because we've already listen()ed on + * the server end (even though we won't accept() the connection + * until later on). + */ + do { + ret = connect(cs, (struct sockaddr *)&csaddr, csaddrlen); + } while (ret < 0 && errno == EINTR); + if (ret < 0) { + closesocket(s); + closesocket(cs); + return 0; + } + pid = fork(); switch(pid) { case -1: error_report("Error: fork failed: %s", strerror(errno)); + closesocket(cs); close(s); return 0; @@ -131,21 +157,10 @@ fork_exec(struct socket *so, const char *ex, int do_pty) setsid(); /* Set the DISPLAY */ - getsockname(s, (struct sockaddr *)&addr, &addrlen); close(s); - /* - * Connect to the socket - * XXX If any of these fail, we're in trouble! - */ - s = qemu_socket(AF_INET, SOCK_STREAM, 0); - addr.sin_addr = loopback_addr; - do { - ret = connect(s, (struct sockaddr *)&addr, addrlen); - } while (ret < 0 && errno == EINTR); - - dup2(s, 0); - dup2(s, 1); - dup2(s, 2); + dup2(cs, 0); + dup2(cs, 1); + dup2(cs, 2); for (s = getdtablesize() - 1; s >= 3; s--) close(s); @@ -178,12 +193,10 @@ fork_exec(struct socket *so, const char *ex, int do_pty) default: qemu_add_child_watch(pid); + closesocket(cs); /* - * XXX this could block us... - * XXX Should set a timer here, and if accept() doesn't - * return after X seconds, declare it a failure - * The only reason this will block forever is if socket() - * of connect() fail in the child process + * This should never block, because we already connect()ed + * on the child end before we forked. */ do { so->s = accept(s, (struct sockaddr *)&addr, &addrlen);