When relocating fds, update the debug fd if it is set so we are

guaranteed to get debugging output.

3 files changed, 24 insertions, 1 deletions

diff --git a/common/sudo_debug.c b/common/sudo_debug.c
index 2f542a352..ed842bc62 100644
--- a/common/sudo_debug.c
+++ b/common/sudo_debug.c
@@ -570,3 +570,19 @@ sudo_debug_fd_get(void)
 {
     return sudo_debug_fd;
 }
+
+/*
+ * Setter for the debug descriptor.
+ */
+int
+sudo_debug_fd_set(int fd)
+{
+    if (sudo_debug_fd != -1 && fd != sudo_debug_fd) {
+	if (dup2(sudo_debug_fd, fd) == -1)
+	    return -1;
+	(void)fcntl(fd, F_SETFD, FD_CLOEXEC);
+	close(sudo_debug_fd);
+	sudo_debug_fd = fd;
+    }
+    return sudo_debug_fd;
+}
diff --git a/include/sudo_debug.h b/include/sudo_debug.h
index f781dc0b3..31be22d09 100644
--- a/include/sudo_debug.h
+++ b/include/sudo_debug.h
@@ -219,6 +219,7 @@ void sudo_debug_exit_str(const char *func, const char *file, int line, int subsy
 void sudo_debug_exit_str_masked(const char *func, const char *file, int line, int subsys, const char *rval);
 void sudo_debug_exit_ptr(const char *func, const char *file, int line, int subsys, const void *rval);
 int sudo_debug_fd_get(void);
+int sudo_debug_fd_set(int fd);
 int sudo_debug_init(const char *debugfile, const char *settings);
 void sudo_debug_printf_nvm(int pri, const char *fmt, ...) __printf0like(2, 3);
 void sudo_debug_printf2(const char *func, const char *file, int line, int level, const char *fmt, ...) __printf0like(5, 6);
diff --git a/src/preserve_fds.c b/src/preserve_fds.c
index 981ac2066..d5c1fce7d 100644
--- a/src/preserve_fds.c
+++ b/src/preserve_fds.c
@@ -99,11 +99,13 @@ add_preserved_fd(struct preserved_fd_list *pfds, int fd)
 void
 closefrom_except(int startfd, struct preserved_fd_list *pfds)
 {
-    int fd, lastfd = -1;
+    int debug_fd, fd, lastfd = -1;
     struct preserved_fd *pfd, *pfd_next;
     fd_set *fdsp;
     debug_decl(closefrom_except, SUDO_DEBUG_UTIL)
 
+    debug_fd = sudo_debug_fd_get();
+
     /* First, relocate preserved fds to be as contiguous as possible.  */
     TAILQ_FOREACH_REVERSE_SAFE(pfd, pfds, preserved_fd_list, entries, pfd_next) {
 	if (pfd->highfd < startfd)
@@ -117,6 +119,8 @@ closefrom_except(int startfd, struct preserved_fd_list *pfds)
 	    }
 	    pfd->lowfd = fd;
 	    fd = pfd->highfd;
+	    if (fd == debug_fd)
+		debug_fd = sudo_debug_fd_set(pfd->lowfd);
 	    sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
 		"dup %d -> %d", pfd->highfd, pfd->lowfd);
 	}
@@ -182,6 +186,8 @@ closefrom_except(int startfd, struct preserved_fd_list *pfds)
 		sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
 		    "fcntl(%d, F_SETFD, %d)", pfd->highfd, pfd->flags);
 	    }
+	    if (pfd->lowfd == debug_fd)
+		debug_fd = sudo_debug_fd_set(pfd->highfd);
 	    (void) close(pfd->lowfd);
 	}
     }