When the closefrom limit is greater than any of the preserved fds,

the pfds list will be non-empty but lastfd will be -1 triggering
an ecalloc(0) assertion.  Instead, test for lastfd being -1 and
make sure we always update it, even if dup() fails.
Also restore initial value of lowfd after we are done relocating.
Fixes bug #633

diff --git a/src/preserve_fds.c b/src/preserve_fds.c
index d5c1fce7d0ea8e2c84f86f7ab71aaf41bcec493f..587fb88c3aa39fa683ddffbc9e2b313951898ef8 100644 (file)
--- a/src/preserve_fds.c
+++ b/src/preserve_fds.c
@@ -111,12 +111,15 @@ closefrom_except(int startfd, struct preserved_fd_list *pfds)
        if (pfd->highfd < startfd)
            continue;
        fd = dup(pfd->highfd);
-       if (fd < pfd->highfd) {
-           if (fd == -1) {
-               if (errno == EBADF)
-                   TAILQ_REMOVE(pfds, pfd, entries);
+       if (fd == -1) {
+           sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
+               "dup %d", pfd->highfd);
+           if (errno == EBADF) {
+               TAILQ_REMOVE(pfds, pfd, entries);
                continue;
            }
+           /* NOTE: still need to adjust lastfd below with unchanged lowfd. */
+       } else if (fd < pfd->highfd) {
            pfd->lowfd = fd;
            fd = pfd->highfd;
            if (fd == debug_fd)
@@ -124,13 +127,14 @@ closefrom_except(int startfd, struct preserved_fd_list *pfds)
            sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
                "dup %d -> %d", pfd->highfd, pfd->lowfd);
        }
-       (void) close(fd);
+       if (fd != -1)
+           (void) close(fd);
 
        if (pfd->lowfd > lastfd)
            lastfd = pfd->lowfd;        /* highest (relocated) preserved fd */
     }
 
-    if (TAILQ_EMPTY(pfds)) {
+    if (lastfd == -1) {
        /* No fds to preserve. */
        sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
            "closefrom(%d)", startfd);
@@ -146,7 +150,6 @@ closefrom_except(int startfd, struct preserved_fd_list *pfds)
 
     /*
      * Close any unpreserved fds [startfd,lastfd]
-     * NOTE: this could relocate the debug fd, breaking the debug subsystem.
      */
     for (fd = startfd; fd <= lastfd; fd++) {
        if (!FD_ISSET(fd, fdsp)) {
@@ -189,6 +192,7 @@ closefrom_except(int startfd, struct preserved_fd_list *pfds)
            if (pfd->lowfd == debug_fd)
                debug_fd = sudo_debug_fd_set(pfd->highfd);
            (void) close(pfd->lowfd);
+           pfd->lowfd = pfd->highfd;
        }
     }
     debug_return;