[git commit] telnetd: more compact version of the fix for stray open fds
Denys Vlasenko
vda.linux at googlemail.com
Wed Jun 10 11:38:08 UTC 2009
commit: http://git.busybox.net/busybox/commit/?id=1d77db8459e1948cdde407f5010f772b81048dbd
branch: http://git.busybox.net/busybox/commit/?id=refs/heads/master
function old new delta
telnetd_main 1520 1527 +7
make_new_session 510 416 -94
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 7/-94) Total: -87 bytes
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
networking/telnetd.c | 90 +++++++++++++++++++++----------------------------
1 files changed, 39 insertions(+), 51 deletions(-)
diff --git a/networking/telnetd.c b/networking/telnetd.c
index 6a8190b..540387f 100644
--- a/networking/telnetd.c
+++ b/networking/telnetd.c
@@ -32,11 +32,12 @@
#endif
#include <arpa/telnet.h>
-/* Structure that describes a session */
struct tsession {
struct tsession *next;
pid_t shell_pid;
- int sockfd_read, sockfd_write, ptyfd;
+ int sockfd_read;
+ int sockfd_write;
+ int ptyfd;
/* two circular buffers */
/*char *buf1, *buf2;*/
@@ -125,9 +126,9 @@ remove_iacs(struct tsession *ts, int *pnum_totty)
* TELOPT_NAWS support!
*/
if ((ptr+2) >= end) {
- /* only the beginning of the IAC is in the
+ /* Only the beginning of the IAC is in the
buffer we were asked to process, we can't
- process this char. */
+ process this char */
break;
}
/*
@@ -153,13 +154,13 @@ remove_iacs(struct tsession *ts, int *pnum_totty)
num_totty = totty - ptr0;
*pnum_totty = num_totty;
- /* the difference between ptr and totty is number of iacs
- we removed from the stream. Adjust buf1 accordingly. */
+ /* The difference between ptr and totty is number of iacs
+ we removed from the stream. Adjust buf1 accordingly */
if ((ptr - totty) == 0) /* 99.999% of cases */
return ptr0;
ts->wridx1 += ptr - totty;
ts->size1 -= ptr - totty;
- /* move chars meant for the terminal towards the end of the buffer */
+ /* Move chars meant for the terminal towards the end of the buffer */
return memmove(ptr - num_totty, ptr0, num_totty);
}
@@ -216,7 +217,7 @@ enum {
static struct tsession *
make_new_session(
- IF_FEATURE_TELNETD_STANDALONE(int master_fd, int sock)
+ IF_FEATURE_TELNETD_STANDALONE(int sock)
IF_NOT_FEATURE_TELNETD_STANDALONE(void)
) {
const char *login_argv[2];
@@ -228,18 +229,20 @@ make_new_session(
/*ts->buf1 = (char *)(ts + 1);*/
/*ts->buf2 = ts->buf1 + BUFSIZE;*/
- /* Got a new connection, set up a tty. */
+ /* Got a new connection, set up a tty */
fd = xgetpty(tty_name);
if (fd > G.maxfd)
G.maxfd = fd;
ts->ptyfd = fd;
ndelay_on(fd);
+ close_on_exec_on(fd);
+
#if ENABLE_FEATURE_TELNETD_STANDALONE
- ts->sockfd_read = sock;
/* SO_KEEPALIVE by popular demand */
setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
+ ts->sockfd_read = sock;
ndelay_on(sock);
- if (!sock) { /* We are called with fd 0 - we are in inetd mode */
+ if (sock == 0) { /* We are called with fd 0 - we are in inetd mode */
sock++; /* so use fd 1 for output */
ndelay_on(sock);
}
@@ -254,6 +257,7 @@ make_new_session(
ndelay_on(0);
ndelay_on(1);
#endif
+
/* Make the telnet client understand we will echo characters so it
* should not do it locally. We don't tell the client to run linemode,
* because we want to handle line editing and tab completion and other
@@ -303,42 +307,20 @@ make_new_session(
/* Restore default signal handling ASAP */
bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL);
-#if ENABLE_FEATURE_TELNETD_STANDALONE
- if (!(option_mask32 & OPT_INETD)) {
- struct tsession *tp = G.sessions;
- while (tp) {
- close(tp->ptyfd);
- close(tp->sockfd_read);
- /* sockfd_write == sockfd_read for standalone telnetd */
- /*close(tp->sockfd_write);*/
- tp = tp->next;
- }
- }
-#endif
-
/* Make new session and process group */
setsid();
- close(fd);
-#if ENABLE_FEATURE_TELNETD_STANDALONE
- if (master_fd >= 0)
- close(master_fd);
- close(sock);
-#endif
- /* Open the child's side of the tty. */
+ /* Open the child's side of the tty */
/* NB: setsid() disconnects from any previous ctty's. Therefore
* we must open child's side of the tty AFTER setsid! */
-#if ENABLE_FEATURE_TELNETD_STANDALONE
- if (sock != 0) /* if we did not close 0 already */
-#endif
- close(0);
+ close(0);
xopen(tty_name, O_RDWR); /* becomes our ctty */
xdup2(0, 1);
xdup2(0, 2);
tcsetpgrp(0, getpid()); /* switch this tty's process group to us */
- /* The pseudo-terminal allocated to the client is configured to operate in
- * cooked mode, and with XTABS CRMOD enabled (see tty(4)). */
+ /* The pseudo-terminal allocated to the client is configured to operate
+ * in cooked mode, and with XTABS CRMOD enabled (see tty(4)) */
tcgetattr(0, &termbuf);
termbuf.c_lflag |= ECHO; /* if we use readline we dont want this */
termbuf.c_oflag |= ONLCR | XTABS;
@@ -359,7 +341,10 @@ make_new_session(
login_argv[0] = G.loginpath;
login_argv[1] = NULL;
/* exec busybox applet (if PREFER_APPLETS=y), if that fails,
- * exec external program */
+ * exec external program.
+ * NB: sock is either 0 or has CLOEXEC set on it.
+ * fd has CLOEXEC set on it too. These two fds will be closed here.
+ */
BB_EXECVP(G.loginpath, (char **)login_argv);
/* _exit is safer with vfork, and we shouldn't send message
* to remote clients anyway */
@@ -496,12 +481,13 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
#if ENABLE_FEATURE_TELNETD_STANDALONE
if (IS_INETD) {
- G.sessions = make_new_session(-1, 0);
+ G.sessions = make_new_session(0);
if (!G.sessions) /* pty opening or vfork problem, exit */
return 1; /* make_new_session prints error message */
} else {
master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr);
xlisten(master_fd, 1);
+ close_on_exec_on(master_fd);
}
#else
G.sessions = make_new_session();
@@ -518,8 +504,8 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
signal(SIGCHLD, SIG_IGN);
/*
- This is how the buffers are used. The arrows indicate the movement
- of data.
+ This is how the buffers are used. The arrows indicate data flow.
+
+-------+ wridx1++ +------+ rdidx1++ +----------+
| | <-------------- | buf1 | <-------------- | |
| | size1-- +------+ size1++ | |
@@ -545,7 +531,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
* before each select. Can be a problem with 500+ connections. */
ts = G.sessions;
while (ts) {
- struct tsession *next = ts->next; /* in case we free ts. */
+ struct tsession *next = ts->next; /* in case we free ts */
if (ts->shell_pid == -1) {
/* Child died and we detected that */
free_session(ts);
@@ -575,7 +561,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
goto again; /* EINTR or ENOMEM */
#if ENABLE_FEATURE_TELNETD_STANDALONE
- /* First check for and accept new sessions. */
+ /* Check for and accept new sessions */
if (!IS_INETD && FD_ISSET(master_fd, &rdfdset)) {
int fd;
struct tsession *new_ts;
@@ -583,8 +569,10 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
fd = accept(master_fd, NULL, NULL);
if (fd < 0)
goto again;
- /* Create a new session and link it into our active list */
- new_ts = make_new_session(master_fd, fd);
+ close_on_exec_on(fd);
+
+ /* Create a new session and link it into active list */
+ new_ts = make_new_session(fd);
if (new_ts) {
new_ts->next = G.sessions;
G.sessions = new_ts;
@@ -594,15 +582,15 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
}
#endif
- /* Then check for data tunneling. */
+ /* Then check for data tunneling */
ts = G.sessions;
while (ts) { /* For all sessions... */
- struct tsession *next = ts->next; /* in case we free ts. */
+ struct tsession *next = ts->next; /* in case we free ts */
if (/*ts->size1 &&*/ FD_ISSET(ts->ptyfd, &wrfdset)) {
int num_totty;
unsigned char *ptr;
- /* Write to pty from buffer 1. */
+ /* Write to pty from buffer 1 */
ptr = remove_iacs(ts, &num_totty);
count = safe_write(ts->ptyfd, ptr, num_totty);
if (count < 0) {
@@ -617,7 +605,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
}
skip1:
if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) {
- /* Write to socket from buffer 2. */
+ /* Write to socket from buffer 2 */
count = MIN(BUFSIZE - ts->wridx2, ts->size2);
count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count);
if (count < 0) {
@@ -647,7 +635,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
}
if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) {
- /* Read from socket to buffer 1. */
+ /* Read from socket to buffer 1 */
count = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
count = safe_read(ts->sockfd_read, TS_BUF1(ts) + ts->rdidx1, count);
if (count <= 0) {
@@ -666,7 +654,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
}
skip3:
if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) {
- /* Read from pty to buffer 2. */
+ /* Read from pty to buffer 2 */
count = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count);
if (count <= 0) {
--
1.6.0.6
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