[REDIR] Fix redirect restore on saved file descriptors

As it stands if a redirection occurs on a file descriptor that was
previously closed, it won't be closed after that redirection goes
out of effect.  This is because we don't keep track of closed file
descriptors properly as we do for open ones.

This patch fixes this by introducing two new states, CLOSED and
REALLY_CLOSED.  The first represents an initially closed descriptor
which is now open while the second one represents an initally closed
descriptor which is now closed.

This patch is based on work by Rainer Weikusat.

1 files changed, 37 insertions, 9 deletions

diff --git a/src/redir.c b/src/redir.c
index 6ffde0c..d4d9c39 100644
--- a/src/redir.c
+++ b/src/redir.c
@@ -57,7 +57,10 @@
 #include "error.h"
 
 
+#define REALLY_CLOSED -3	/* fd that was closed and still is */
 #define EMPTY -2		/* marks an unused slot in redirtab */
+#define CLOSED -1		/* fd opened for redir needs to be closed */
+
 #ifndef PIPE_BUF
 # define PIPESIZE 4096		/* amount of buffering in a pipe */
 #else
@@ -135,14 +138,29 @@ redirect(union node *redir, int flags)
 			continue; /* redirect from/to same file descriptor */
 
 		newfd = openredirect(n);
+
+		if (sv) {
+			p = &sv->renamed[fd];
+			i = *p;
+
+			if (likely(i == EMPTY)) {
+				i = CLOSED;
+				if (fd != newfd) {
+					i = savefd(fd);
+					fd = -1;
+				}
+			}
+
+			if (i == newfd)
+				/* Can only happen if i == newfd == CLOSED */
+				i = REALLY_CLOSED;
+
+			*p = i;
+		}
+
 		if (fd == newfd)
 			continue;
-		if (sv && *(p = &sv->renamed[fd]) == EMPTY) {
-			int i = savefd(fd);
 
-			if (i >= 0)
-				*p = i;
-		}
 #ifdef notyet
 		dupredirect(n, newfd, memory);
 #else
@@ -204,7 +222,7 @@ openredirect(union node *redir)
 		/* Fall through to eliminate warning. */
 	case NTOFD:
 	case NFROMFD:
-		f = -1;
+		f = redir->ndup.dupfd;
 		break;
 	case NHERE:
 	case NXHERE:
@@ -239,9 +257,10 @@ dupredirect(redir, f)
 	memory[fd] = 0;
 #endif
 	if (redir->nfile.type == NTOFD || redir->nfile.type == NFROMFD) {
-		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
+		/* if not ">&-" */
+		if (f >= 0) {
 #ifdef notyet
-			if (memory[redir->ndup.dupfd])
+			if (memory[f])
 				memory[fd] = 1;
 			else
 #endif
@@ -324,10 +343,19 @@ popredir(int drop)
 	INTOFF;
 	rp = redirlist;
 	for (i = 0 ; i < 10 ; i++) {
-		if (rp->renamed[i] != EMPTY) {
+		switch (rp->renamed[i]) {
+		case CLOSED:
+			if (!drop)
+				close(i);
+			break;
+		case EMPTY:
+		case REALLY_CLOSED:
+			break;
+		default:
 			if (!drop)
 				dup2(rp->renamed[i], i);
 			close(rp->renamed[i]);
+			break;
 		}
 	}
 	redirlist = rp->next;