ping: do not leak data from stack; shrink

FANCY ping:
function                                             old     new   delta
common_ping_main                                     386    1732   +1346
sendping6                                             98      83     -15
sendping4                                            188     158     -30
ping4                                                575       -    -575
ping6                                                756       -    -756
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 1/2 up/down: 1346/-1376)        Total: -30 bytes

!FANCY ping:
function                                             old     new   delta
hostname                                               4       -      -4
common_ping_main                                     566     499     -67

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 57 insertions, 47 deletions

diff --git a/networking/ping.c b/networking/ping.c
index 467b7f694..6a766a437 100644
--- a/networking/ping.c
+++ b/networking/ping.c
@@ -43,13 +43,12 @@ enum {
         DEFDATALEN = 56,
         MAXIPLEN = 60,
         MAXICMPLEN = 76,
-        MAXPACKET = 65468,
         MAX_DUP_CHK = (8 * 128),
         MAXWAIT = 10,
         PINGINTERVAL = 1, /* 1 second */
 };
 
-/* common routines */
+/* Common routines */
 
 static int in_cksum(unsigned short *buf, int sz)
 {
@@ -76,40 +75,41 @@ static int in_cksum(unsigned short *buf, int sz)
 
 #if !ENABLE_FEATURE_FANCY_PING
 
-/* simple version */
+/* Simple version */
 
-static char *hostname;
+struct globals {
+        char *hostname;
+        char packet[DEFDATALEN + MAXIPLEN + MAXICMPLEN];
+} FIX_ALIASING;
+#define G (*(struct globals*)&bb_common_bufsiz1)
+#define INIT_G() do { } while (0)
 
 static void noresp(int ign UNUSED_PARAM)
 {
-        printf("No response from %s\n", hostname);
+        printf("No response from %s\n", G.hostname);
         exit(EXIT_FAILURE);
 }
 
 static void ping4(len_and_sockaddr *lsa)
 {
-        struct sockaddr_in pingaddr;
         struct icmp *pkt;
         int pingsock, c;
-        char packet[DEFDATALEN + MAXIPLEN + MAXICMPLEN];
 
         pingsock = create_icmp_socket();
-        pingaddr = lsa->u.sin;
 
-        pkt = (struct icmp *) packet;
-        memset(pkt, 0, sizeof(packet));
+        pkt = (struct icmp *) G.packet;
+        memset(pkt, 0, sizeof(G.packet));
         pkt->icmp_type = ICMP_ECHO;
-        pkt->icmp_cksum = in_cksum((unsigned short *) pkt, sizeof(packet));
+        pkt->icmp_cksum = in_cksum((unsigned short *) pkt, sizeof(G.packet));
 
-        c = xsendto(pingsock, packet, DEFDATALEN + ICMP_MINLEN,
-                           (struct sockaddr *) &pingaddr, sizeof(pingaddr));
+        xsendto(pingsock, G.packet, DEFDATALEN + ICMP_MINLEN, &lsa->u.sa, lsa->len);
 
         /* listen for replies */
         while (1) {
                 struct sockaddr_in from;
                 socklen_t fromlen = sizeof(from);
 
-                c = recvfrom(pingsock, packet, sizeof(packet), 0,
+                c = recvfrom(pingsock, G.packet, sizeof(G.packet), 0,
                                 (struct sockaddr *) &from, &fromlen);
                 if (c < 0) {
                         if (errno != EINTR)
@@ -117,9 +117,9 @@ static void ping4(len_and_sockaddr *lsa)
                         continue;
                 }
                 if (c >= 76) {                  /* ip + icmp */
-                        struct iphdr *iphdr = (struct iphdr *) packet;
+                        struct iphdr *iphdr = (struct iphdr *) G.packet;
 
-                        pkt = (struct icmp *) (packet + (iphdr->ihl << 2));     /* skip ip hdr */
+                        pkt = (struct icmp *) (G.packet + (iphdr->ihl << 2));   /* skip ip hdr */
                         if (pkt->icmp_type == ICMP_ECHOREPLY)
                                 break;
                 }
@@ -131,31 +131,27 @@ static void ping4(len_and_sockaddr *lsa)
 #if ENABLE_PING6
 static void ping6(len_and_sockaddr *lsa)
 {
-        struct sockaddr_in6 pingaddr;
         struct icmp6_hdr *pkt;
         int pingsock, c;
         int sockopt;
-        char packet[DEFDATALEN + MAXIPLEN + MAXICMPLEN];
 
         pingsock = create_icmp6_socket();
-        pingaddr = lsa->u.sin6;
 
-        pkt = (struct icmp6_hdr *) packet;
-        memset(pkt, 0, sizeof(packet));
+        pkt = (struct icmp6_hdr *) G.packet;
+        memset(pkt, 0, sizeof(G.packet));
         pkt->icmp6_type = ICMP6_ECHO_REQUEST;
 
         sockopt = offsetof(struct icmp6_hdr, icmp6_cksum);
         setsockopt(pingsock, SOL_RAW, IPV6_CHECKSUM, &sockopt, sizeof(sockopt));
 
-        c = xsendto(pingsock, packet, DEFDATALEN + sizeof (struct icmp6_hdr),
-                           (struct sockaddr *) &pingaddr, sizeof(pingaddr));
+        xsendto(pingsock, G.packet, DEFDATALEN + sizeof(struct icmp6_hdr), &lsa->u.sa, lsa->len);
 
         /* listen for replies */
         while (1) {
                 struct sockaddr_in6 from;
                 socklen_t fromlen = sizeof(from);
 
-                c = recvfrom(pingsock, packet, sizeof(packet), 0,
+                c = recvfrom(pingsock, G.packet, sizeof(G.packet), 0,
                                 (struct sockaddr *) &from, &fromlen);
                 if (c < 0) {
                         if (errno != EINTR)
@@ -163,7 +159,7 @@ static void ping6(len_and_sockaddr *lsa)
                         continue;
                 }
                 if (c >= ICMP_MINLEN) {                 /* icmp6_hdr */
-                        pkt = (struct icmp6_hdr *) packet;
+                        pkt = (struct icmp6_hdr *) G.packet;
                         if (pkt->icmp6_type == ICMP6_ECHO_REPLY)
                                 break;
                 }
@@ -180,6 +176,8 @@ static int common_ping_main(sa_family_t af, char **argv)
 {
         len_and_sockaddr *lsa;
 
+        INIT_G();
+
 #if ENABLE_PING6
         while ((++argv)[0] && argv[0][0] == '-') {
                 if (argv[0][1] == '4') {
@@ -196,14 +194,14 @@ static int common_ping_main(sa_family_t af, char **argv)
         argv++;
 #endif
 
-        hostname = *argv;
-        if (!hostname)
+        G.hostname = *argv;
+        if (!G.hostname)
                 bb_show_usage();
 
 #if ENABLE_PING6
-        lsa = xhost_and_af2sockaddr(hostname, 0, af);
+        lsa = xhost_and_af2sockaddr(G.hostname, 0, af);
 #else
-        lsa = xhost_and_af2sockaddr(hostname, 0, AF_INET);
+        lsa = xhost_and_af2sockaddr(G.hostname, 0, AF_INET);
 #endif
         /* Set timer _after_ DNS resolution */
         signal(SIGALRM, noresp);
@@ -215,7 +213,7 @@ static int common_ping_main(sa_family_t af, char **argv)
         else
 #endif
                 ping4(lsa);
-        printf("%s is alive!\n", hostname);
+        printf("%s is alive!\n", G.hostname);
         return EXIT_SUCCESS;
 }
 
@@ -223,7 +221,7 @@ static int common_ping_main(sa_family_t af, char **argv)
 #else /* FEATURE_FANCY_PING */
 
 
-/* full(er) version */
+/* Full(er) version */
 
 #define OPT_STRING ("qvc:s:w:W:I:4" IF_PING6("6"))
 enum {
@@ -253,6 +251,9 @@ struct globals {
         unsigned deadline;
         unsigned timeout;
         unsigned total_secs;
+        unsigned sizeof_rcv_packet;
+        char *rcv_packet; /* [datalen + MAXIPLEN + MAXICMPLEN] */
+        void *snd_packet; /* [datalen + ipv4/ipv6_const] */
         const char *hostname;
         const char *dotted;
         union {
@@ -370,19 +371,20 @@ static void sendping_tail(void (*sp)(int), const void *pkt, int size_pkt)
 
 static void sendping4(int junk UNUSED_PARAM)
 {
-        /* +4 reserves a place for timestamp, which may end up sitting
-         * *after* packet. Saves one if() */
-        struct icmp *pkt = alloca(datalen + ICMP_MINLEN + 4);
+        struct icmp *pkt = G.snd_packet;
 
-        memset(pkt, 0, datalen + ICMP_MINLEN + 4);
+        //memset(pkt, 0, datalen + ICMP_MINLEN + 4); - G.snd_packet was xzalloced
         pkt->icmp_type = ICMP_ECHO;
         /*pkt->icmp_code = 0;*/
-        /*pkt->icmp_cksum = 0;*/
+        pkt->icmp_cksum = 0; /* cksum is calculated with this field set to 0 */
         pkt->icmp_seq = htons(ntransmitted); /* don't ++ here, it can be a macro */
         pkt->icmp_id = myid;
 
-        /* We don't do hton, because we will read it back on the same machine */
+        /* If datalen < 4, we store timestamp _past_ the packet,
+         * but it's ok - we allocated 4 extra bytes in xzalloc() just in case.
+         */
         /*if (datalen >= 4)*/
+                /* No hton: we'll read it back on the same machine */
                 *(uint32_t*)&pkt->icmp_dun = monotonic_us();
 
         pkt->icmp_cksum = in_cksum((unsigned short *) pkt, datalen + ICMP_MINLEN);
@@ -394,7 +396,7 @@ static void sendping6(int junk UNUSED_PARAM)
 {
         struct icmp6_hdr *pkt = alloca(datalen + sizeof(struct icmp6_hdr) + 4);
 
-        memset(pkt, 0, datalen + sizeof(struct icmp6_hdr) + 4);
+        //memset(pkt, 0, datalen + sizeof(struct icmp6_hdr) + 4);
         pkt->icmp6_type = ICMP6_ECHO_REQUEST;
         /*pkt->icmp6_code = 0;*/
         /*pkt->icmp6_cksum = 0;*/
@@ -404,6 +406,8 @@ static void sendping6(int junk UNUSED_PARAM)
         /*if (datalen >= 4)*/
                 *(uint32_t*)(&pkt->icmp6_data8[4]) = monotonic_us();
 
+        //TODO? pkt->icmp_cksum = in_cksum(...);
+
         sendping_tail(sendping6, pkt, datalen + sizeof(struct icmp6_hdr));
 }
 #endif
@@ -561,7 +565,6 @@ static void unpack6(char *packet, int sz, /*struct sockaddr_in6 *from,*/ int hop
 
 static void ping4(len_and_sockaddr *lsa)
 {
-        char packet[datalen + MAXIPLEN + MAXICMPLEN];
         int sockopt;
 
         pingsock = create_icmp_socket();
@@ -594,14 +597,14 @@ static void ping4(len_and_sockaddr *lsa)
                 socklen_t fromlen = (socklen_t) sizeof(from);
                 int c;
 
-                c = recvfrom(pingsock, packet, sizeof(packet), 0,
+                c = recvfrom(pingsock, G.rcv_packet, G.sizeof_rcv_packet, 0,
                                 (struct sockaddr *) &from, &fromlen);
                 if (c < 0) {
                         if (errno != EINTR)
                                 bb_perror_msg("recvfrom");
                         continue;
                 }
-                unpack4(packet, c, &from);
+                unpack4(G.rcv_packet, c, &from);
                 if (pingcount && nreceived >= pingcount)
                         break;
         }
@@ -610,7 +613,6 @@ static void ping4(len_and_sockaddr *lsa)
 extern int BUG_bad_offsetof_icmp6_cksum(void);
 static void ping6(len_and_sockaddr *lsa)
 {
-        char packet[datalen + MAXIPLEN + MAXICMPLEN];
         int sockopt;
         struct msghdr msg;
         struct sockaddr_in6 from;
@@ -670,8 +672,8 @@ static void ping6(len_and_sockaddr *lsa)
         msg.msg_iov = &iov;
         msg.msg_iovlen = 1;
         msg.msg_control = control_buf;
-        iov.iov_base = packet;
-        iov.iov_len = sizeof(packet);
+        iov.iov_base = G.rcv_packet;
+        iov.iov_len = G.sizeof_rcv_packet;
         while (1) {
                 int c;
                 struct cmsghdr *mp;
@@ -694,7 +696,7 @@ static void ping6(len_and_sockaddr *lsa)
                                 move_from_unaligned_int(hoplimit, CMSG_DATA(mp));
                         }
                 }
-                unpack6(packet, c, /*&from,*/ hoplimit);
+                unpack6(G.rcv_packet, c, /*&from,*/ hoplimit);
                 if (pingcount && nreceived >= pingcount)
                         break;
         }
@@ -710,12 +712,20 @@ static void ping(len_and_sockaddr *lsa)
         }
         printf(": %d data bytes\n", datalen);
 
+        G.sizeof_rcv_packet = datalen + MAXIPLEN + MAXICMPLEN;
+        G.rcv_packet = xzalloc(G.sizeof_rcv_packet);
 #if ENABLE_PING6
-        if (lsa->u.sa.sa_family == AF_INET6)
+        if (lsa->u.sa.sa_family == AF_INET6) {
+                /* +4 reserves a place for timestamp, which may end up sitting
+                 * _after_ packet. Saves one if() - see sendping4/6() */
+                G.snd_packet = xzalloc(datalen + sizeof(struct icmp6_hdr) + 4);
                 ping6(lsa);
-        else
+        } else
 #endif
+        {
+                G.snd_packet = xzalloc(datalen + ICMP_MINLEN + 4);
                 ping4(lsa);
+        }
 }
 
 static int common_ping_main(int opt, char **argv)