ash: fix execution of shell scripts without shebang

We were assuming #!/bin/sh, whereas we had to simply re-enter ash.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/shell/ash.c b/shell/ash.c
index c3c9536..09db046 100644 (file)
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -7396,8 +7396,6 @@ static int builtinloc = -1;     /* index in path of %builtin, or -1 */
 static void
 tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) char *cmd, char **argv, char **envp)
 {
-       int repeated = 0;
-
 #if ENABLE_FEATURE_SH_STANDALONE
        if (applet_no >= 0) {
                if (APPLET_IS_NOEXEC(applet_no)) {
@@ -7421,25 +7419,36 @@ tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) char *cmd, char **argv, char **
 #else
        execve(cmd, argv, envp);
 #endif
-       if (repeated) {
+       if (cmd == (char*) bb_busybox_exec_path) {
+               /* We already visited ENOEXEC branch below, don't do it again */
+//TODO: try execve(initial_argv0_of_shell, argv, envp) before giving up?
                free(argv);
                return;
        }
        if (errno == ENOEXEC) {
+               /* Run "cmd" as a shell script:
+                * http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
+                * "If the execve() function fails with ENOEXEC, the shell
+                * shall execute a command equivalent to having a shell invoked
+                * with the command name as its first operand,
+                * with any remaining arguments passed to the new shell"
+                *
+                * That is, do not use $SHELL, user's shell, or /bin/sh;
+                * just call ourselves.
+                */
                char **ap;
                char **new;
 
                for (ap = argv; *ap; ap++)
                        continue;
-               ap = new = ckmalloc((ap - argv + 2) * sizeof(ap[0]));
-               ap[1] = cmd;
-               ap[0] = cmd = (char *)DEFAULT_SHELL;
-               ap += 2;
-               argv++;
-               while ((*ap++ = *argv++) != NULL)
+               new = ckmalloc((ap - argv + 2) * sizeof(new[0]));
+               new[0] = (char*) "ash";
+               new[1] = cmd;
+               ap = new + 2;
+               while ((*ap++ = *++argv) != NULL)
                        continue;
+               cmd = (char*) bb_busybox_exec_path;
                argv = new;
-               repeated++;
                goto repeat;
        }
 }