crontab: do not destroy STDIN_FILENO, editor may need it (crontab -e)

vi: deal with EOF/error on stdin and with input NULs

function                                             old     new   delta
crontab_main                                         623     642     +19
edit_file                                            901     906      +5
readit                                               331     318     -13

2 files changed, 35 insertions, 32 deletions

diff --git a/editors/vi.c b/editors/vi.c
index 27f2a3abd..02bdbb37b 100644
--- a/editors/vi.c
+++ b/editors/vi.c
@@ -147,10 +147,10 @@ struct globals {
 #endif
 
         smallint editing;        // >0 while we are editing a file
-                                 // [code audit says "can be 0 or 1 only"]
+                                 // [code audit says "can be 0, 1 or 2 only"]
         smallint cmd_mode;       // 0=command  1=insert 2=replace
         int file_modified;       // buffer contents changed (counter, not flag!)
-        int last_file_modified; // = -1;
+        int last_file_modified;  // = -1;
         int fn_start;            // index of first cmd line file name
         int save_argc;           // how many file names on cmd line
         int cmdcnt;              // repetition count
@@ -623,7 +623,7 @@ static void edit_file(char *fn)
                 // These are commands that change text[].
                 // Remember the input for the "." command
                 if (!adding2q && ioq_start == NULL
-                 && strchr(modifying_cmds, c)
+                 && c != '\0' && strchr(modifying_cmds, c)
                 ) {
                         start_new_cmd_q(c);
                 }
@@ -645,8 +645,8 @@ static void edit_file(char *fn)
         }
         //-------------------------------------------------------------------
 
-        place_cursor(rows, 0, FALSE);   // go to bottom of screen
-        clear_to_eol();         // Erase to end of line
+        place_cursor(rows - 1, 0, FALSE); // go to bottom of screen
+        clear_to_eol(); // erase to end of line
         cookmode();
 #undef cur_line
 }
@@ -2009,9 +2009,9 @@ static void start_new_cmd_q(char c)
 {
         // get buffer for new cmd
         // if there is a current cmd count put it in the buffer first
-        if (cmdcnt > 0)
+        if (cmdcnt > 0) {
                 lmc_len = sprintf(last_modifying_cmd, "%d%c", cmdcnt, c);
-        else { // just save char c onto queue
+        } else { // just save char c onto queue
                 last_modifying_cmd[0] = c;
                 lmc_len = 1;
         }
@@ -2157,21 +2157,21 @@ static void winch_sig(int sig UNUSED_PARAM)
 //----- Come here when we get a continue signal -------------------
 static void cont_sig(int sig UNUSED_PARAM)
 {
-        rawmode();                      // terminal to "raw"
-        last_status_cksum = 0;  // force status update
-        redraw(TRUE);           // re-draw the screen
+        rawmode(); // terminal to "raw"
+        last_status_cksum = 0; // force status update
+        redraw(TRUE); // re-draw the screen
 
         signal(SIGTSTP, suspend_sig);
         signal(SIGCONT, SIG_DFL);
-        kill(my_pid, SIGCONT);
+        kill(my_pid, SIGCONT); // huh? why? we are already "continued"...
 }
 
 //----- Come here when we get a Suspend signal -------------------
 static void suspend_sig(int sig UNUSED_PARAM)
 {
-        place_cursor(rows - 1, 0, FALSE);       // go to bottom of screen
-        clear_to_eol();         // Erase to end of line
-        cookmode();                     // terminal to "cooked"
+        place_cursor(rows - 1, 0, FALSE); // go to bottom of screen
+        clear_to_eol(); // erase to end of line
+        cookmode(); // terminal to "cooked"
 
         signal(SIGCONT, cont_sig);
         signal(SIGTSTP, SIG_DFL);
@@ -2247,18 +2247,20 @@ static char readit(void)	// read (maybe cursor) key from stdin
 
         fflush(stdout);
         n = chars_to_parse;
-        // get input from User- are there already input chars in Q?
+        // get input from User - are there already input chars in Q?
         if (n <= 0) {
                 // the Q is empty, wait for a typed char
+ again:
                 n = safe_read(STDIN_FILENO, readbuffer, sizeof(readbuffer));
-                if (n < 0) {
-                        if (errno == EBADF || errno == EFAULT || errno == EINVAL
-                         || errno == EIO)
-                                editing = 0; // want to exit
-                        errno = 0;
-                }
-                if (n <= 0)
-                        return 0;       // error
+                if (n <= 0) {
+                        place_cursor(rows - 1, 0, FALSE); // go to bottom of screen
+                        clear_to_eol(); // erase to end of line
+                        cookmode(); // terminal to "cooked"
+                        bb_error_msg_and_die("can't read user input");
+                }
+                /* elsewhere we can get very confused by NULs */
+                if (readbuffer[0] == '\0')
+                        goto again;
                 if (readbuffer[0] == 27) {
                         // This is an ESC char. Is this Esc sequence?
                         // Could be bare Esc key. See if there are any
diff --git a/miscutils/crontab.c b/miscutils/crontab.c
index ef6d94375..673b558c3 100644
--- a/miscutils/crontab.c
+++ b/miscutils/crontab.c
@@ -93,6 +93,7 @@ int crontab_main(int argc UNUSED_PARAM, char **argv)
         char *new_fname;
         char *user_name;  /* -u USER */
         int fd;
+        int src_fd;
         int opt_ler;
 
         /* file [opts]     Replace crontab from file
@@ -144,15 +145,15 @@ int crontab_main(int argc UNUSED_PARAM, char **argv)
                 bb_show_usage();
 
         /* Read replacement file under user's UID/GID/group vector */
+        src_fd = STDIN_FILENO;
         if (!opt_ler) { /* Replace? */
                 if (!argv[0])
                         bb_show_usage();
                 if (NOT_LONE_DASH(argv[0])) {
-                        fd = open_as_user(pas, argv[0]);
-                        if (fd < 0)
+                        src_fd = open_as_user(pas, argv[0]);
+                        if (src_fd < 0)
                                 bb_error_msg_and_die("user %s cannot read %s",
                                                 pas->pw_name, argv[0]);
-                        xmove_fd(fd, STDIN_FILENO);
                 }
         }
 
@@ -180,23 +181,23 @@ int crontab_main(int argc UNUSED_PARAM, char **argv)
                 tmp_fname = xasprintf("%s.%u", crontab_dir, (unsigned)getpid());
                 /* No O_EXCL: we don't want to be stuck if earlier crontabs
                  * were killed, leaving stale temp file behind */
-                fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC, 0600);
-                xmove_fd(fd, STDIN_FILENO);
-                fchown(STDIN_FILENO, pas->pw_uid, pas->pw_gid);
+                src_fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC, 0600);
+                fchown(src_fd, pas->pw_uid, pas->pw_gid);
                 fd = open(pas->pw_name, O_RDONLY);
                 if (fd >= 0) {
-                        bb_copyfd_eof(fd, STDIN_FILENO);
+                        bb_copyfd_eof(fd, src_fd);
                         close(fd);
+                        xlseek(src_fd, 0, SEEK_SET);
                 }
+                close_on_exec_on(src_fd); /* don't want editor to see this fd */
                 edit_file(pas, tmp_fname);
-                xlseek(STDIN_FILENO, 0, SEEK_SET);
                 /* fall through */
 
         case 0: /* Replace (no -l, -e, or -r were given) */
                 new_fname = xasprintf("%s.new", pas->pw_name);
                 fd = open(new_fname, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 0600);
                 if (fd >= 0) {
-                        bb_copyfd_eof(STDIN_FILENO, fd);
+                        bb_copyfd_eof(src_fd, fd);
                         close(fd);
                         xrename(new_fname, pas->pw_name);
                 } else {