ash: fix bug where redirection of closed fd was leaving it open afterwards.

redirect                                             983    1024     +41
bb_echo                                              276     301     +25
popredir                                             118     132     +14
evalcommand                                         1163    1176     +13
bbunpack                                             358     366      +8
echocmd                                               13       5      -8
echo_main                                             13       5      -8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/2 up/down: 101/-16)            Total: 85 bytes
   text    data     bss     dec     hex filename
 774999     962    9236  785197   bfb2d busybox_old
 775084     962    9236  785282   bfb82 busybox_unstripped

coreutils/echo.c

@@ -25,7 +25,9 @@
 
 #include "libbb.h"
 
-int bb_echo(char **argv)
+/* argc is unused, but removing it precludes compiler from
+ * using call -> jump optimization */
+int bb_echo(int argc, char **argv)
 {
 	const char *arg;
 #if !ENABLE_FEATURE_FANCY_ECHO
@@ -33,6 +35,18 @@ int bb_echo(char **argv)
 		eflag = '\\',
 		nflag = 1,  /* 1 -- print '\n' */
 	};
+
+	/* We must check that stdout is not closed.
+	 * The reason for this is highly non-obvious.
+	 * bb_echo is used from shell. Shell must correctly handle "echo foo"
+	 * if stdout is closed. With stdio, output gets shoveled into
+	 * stdout buffer, and even fflush cannot clear it out. It seems that
+	 * even if libc receives EBADF on write attempts, it feels determined
+	 * to output data no matter what. So it will try later,
+	 * and possibly will clobber future output. Not good. */
+	if (dup2(1, 1) != 1)
+		return -1;
+
 	arg = *++argv;
 	if (!arg)
 		goto newline_ret;
@@ -41,6 +55,10 @@ int bb_echo(char **argv)
 	char nflag = 1;
 	char eflag = 0;
 
+	/* We must check that stdout is not closed. */
+	if (dup2(1, 1) != 1)
+		return -1;
+
 	while (1) {
 		arg = *++argv;
 		if (!arg)
@@ -122,7 +140,7 @@ int bb_echo(char **argv)
 int echo_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int echo_main(int argc, char **argv)
 {
-	return bb_echo(argv);
+	return bb_echo(argc, argv);
 }
 
 /*-
@@ -163,3 +181,122 @@ int echo_main(int argc, char **argv)
  *
  *	@(#)echo.c	8.1 (Berkeley) 5/31/93
  */
+
+#ifdef VERSION_WITH_WRITEV
+/* We can't use stdio.
+ * The reason for this is highly non-obvious.
+ * bb_echo is used from shell. Shell must correctly handle "echo foo"
+ * if stdout is closed. With stdio, output gets shoveled into
+ * stdout buffer, and even fflush cannot clear it out. It seems that
+ * even if libc receives EBADF on write attempts, it feels determined
+ * to output data no matter what. So it will try later,
+ * and possibly will clobber future output. Not good.
+ *
+ * Using writev instead, with 'direct' conversion of argv vector.
+ */
+
+int bb_echo(int argc, char **argv)
+{
+	struct iovec io[argc];
+	struct iovec *cur_io = io;
+	char *arg;
+	char *p;
+#if !ENABLE_FEATURE_FANCY_ECHO
+	enum {
+		eflag = '\\',
+		nflag = 1,  /* 1 -- print '\n' */
+	};
+	arg = *++argv;
+	if (!arg)
+		goto newline_ret;
+#else
+	char nflag = 1;
+	char eflag = 0;
+
+	while (1) {
+		arg = *++argv;
+		if (!arg)
+			goto newline_ret;
+		if (*arg != '-')
+			break;
+
+		/* If it appears that we are handling options, then make sure
+		 * that all of the options specified are actually valid.
+		 * Otherwise, the string should just be echoed.
+		 */
+		p = arg + 1;
+		if (!*p)	/* A single '-', so echo it. */
+			goto just_echo;
+
+		do {
+			if (!strrchr("neE", *p))
+				goto just_echo;
+		} while (*++p);
+
+		/* All of the options in this arg are valid, so handle them. */
+		p = arg + 1;
+		do {
+			if (*p == 'n')
+				nflag = 0;
+			if (*p == 'e')
+				eflag = '\\';
+		} while (*++p);
+	}
+ just_echo:
+#endif
+
+	while (1) {
+		/* arg is already == *argv and isn't NULL */
+		int c;
+
+		cur_io->iov_base = p = arg;
+
+		if (!eflag) {
+			/* optimization for very common case */
+			p += strlen(arg);
+		} else while ((c = *arg++)) {
+			if (c == eflag) {	/* Check for escape seq. */
+				if (*arg == 'c') {
+					/* '\c' means cancel newline and
+					 * ignore all subsequent chars. */
+					cur_io->iov_len = p - (char*)cur_io->iov_base;
+					cur_io++;
+					goto ret;
+				}
+#if !ENABLE_FEATURE_FANCY_ECHO
+				/* SUSv3 specifies that octal escapes must begin with '0'. */
+				if ( (((unsigned char)*arg) - '1') >= 7)
+#endif
+				{
+					/* Since SUSv3 mandates a first digit of 0, 4-digit octals
+					* of the form \0### are accepted. */
+					if (*arg == '0' && ((unsigned char)(arg[1]) - '0') < 8) {
+						arg++;
+					}
+					/* bb_process_escape_sequence can handle nul correctly */
+					c = bb_process_escape_sequence( (void*) &arg);
+				}
+			}
+			*p++ = c;
+		}
+
+		arg = *++argv;
+		if (arg)
+			*p++ = ' ';
+		cur_io->iov_len = p - (char*)cur_io->iov_base;
+		cur_io++;
+		if (!arg)
+			break;
+	}
+
+ newline_ret:
+	if (nflag) {
+		cur_io->iov_base = (char*)"\n";
+		cur_io->iov_len = 1;
+		cur_io++;
+	}
+ ret:
+	/* TODO: implement and use full_writev? */
+	return writev(1, io, (cur_io - io)) >= 0; 
+}
+#endif

include/libbb.h

@@ -728,7 +728,7 @@ extern void bb_verror_msg(const char *s, va_list p, const char *strerr);
 
 /* applets which are useful from another applets */
 int bb_cat(char** argv);
-int bb_echo(char** argv);
+int bb_echo(int argc, char** argv);
 int test_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int kill_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 #if ENABLE_ROUTE

shell/ash.c

@@ -4567,6 +4567,7 @@ stoppedjobs(void)
  */
 
 #define EMPTY -2                /* marks an unused slot in redirtab */
+#define CLOSED -3               /* marks a slot of previously-closed fd */
 #ifndef PIPE_BUF
 # define PIPESIZE 4096          /* amount of buffering in a pipe */
 #else
@@ -4791,7 +4792,7 @@ redirect(union node *redir, int flags)
 	int i;
 	int fd;
 	int newfd;
-	int *p;
+
 	nullredirs++;
 	if (!redir) {
 		return;
@@ -4799,15 +4800,13 @@ redirect(union node *redir, int flags)
 	sv = NULL;
 	INT_OFF;
 	if (flags & REDIR_PUSH) {
-		struct redirtab *q;
+		sv = ckmalloc(sizeof(*sv));
-		q = ckmalloc(sizeof(struct redirtab));
+		sv->next = redirlist;
-		q->next = redirlist;
+		redirlist = sv;
-		redirlist = q;
+		sv->nullredirs = nullredirs - 1;
-		q->nullredirs = nullredirs - 1;
 		for (i = 0; i < 10; i++)
-			q->renamed[i] = EMPTY;
+			sv->renamed[i] = EMPTY;
 		nullredirs = 0;
-		sv = q;
 	}
 	n = redir;
 	do {
@@ -4817,9 +4816,14 @@ redirect(union node *redir, int flags)
 			continue; /* redirect from/to same file descriptor */
 
 		newfd = openredirect(n);
-		if (fd == newfd)
+		if (fd == newfd) {
+			/* Descriptor wasn't open before redirect.
+			 * Mark it for close in the future */
+			if (sv && sv->renamed[fd] == EMPTY)
+				sv->renamed[fd] = CLOSED;
 			continue;
-		if (sv && *(p = &sv->renamed[fd]) == EMPTY) {
+		}
+		if (sv && sv->renamed[fd] == EMPTY) {
 			i = fcntl(fd, F_DUPFD, 10);
 
 			if (i == -1) {
@@ -4831,7 +4835,7 @@ redirect(union node *redir, int flags)
 					/* NOTREACHED */
 				}
 			} else {
-				*p = i;
+				sv->renamed[fd] = i;
 				close(fd);
 			}
 		} else {
@@ -4840,7 +4844,7 @@ redirect(union node *redir, int flags)
 		dupredirect(n, newfd);
 	} while ((n = n->nfile.next));
 	INT_ON;
-	if (flags & REDIR_SAVEFD2 && sv && sv->renamed[2] >= 0)
+	if ((flags & REDIR_SAVEFD2) && sv && sv->renamed[2] >= 0)
 		preverrout_fd = sv->renamed[2];
 }
 
@@ -4858,6 +4862,11 @@ popredir(int drop)
 	INT_OFF;
 	rp = redirlist;
 	for (i = 0; i < 10; i++) {
+		if (rp->renamed[i] == CLOSED) {
+			if (!drop)
+				close(i);
+			continue;
+		}
 		if (rp->renamed[i] != EMPTY) {
 			if (!drop) {
 				close(i);
@@ -10994,7 +11003,7 @@ exitcmd(int argc, char **argv)
 static int
 echocmd(int argc, char **argv)
 {
-	return bb_echo(argv);
+	return bb_echo(argc, argv);
 }
 #endif
 

shell/ash_test/ash-redir/redir.right

@@ -0,0 +1 @@
+TEST

shell/ash_test/ash-redir/redir.tests

@@ -0,0 +1,6 @@
+# test: closed fds should stay closed
+exec 1>&-
+echo TEST >TEST
+echo JUNK # lost: stdout is closed
+cat TEST >&2
+rm TEST