[patch] kern/exec_script: return error when the shell name is not specified

[Maxim Pugachev]

Hi,

In a case when the shell name is not specified (i.e. just "#!" without
a path), don't run the heavy logic that checks shell, simply return
ENOENT.

Also, as a tiny improvement: avoid a loop when calculating shell's args length.


Index: sys/kern/exec_script.c
===================================================================
RCS file: /cvs/src/sys/kern/exec_script.c,v
retrieving revision 1.36
diff -u -p -r1.36 exec_script.c
--- sys/kern/exec_script.c      10 Sep 2015 18:10:35 -0000      1.36
+++ sys/kern/exec_script.c      12 Dec 2015 21:18:22 -0000
@@ -69,7 +69,7 @@ exec_script_makecmds(struct proc *p, str
 {
        int error, hdrlinelen, shellnamelen, shellarglen;
        char *hdrstr = epp->ep_hdr;
-       char *cp, *shellname, *shellarg, *oldpnbuf;
+       char *cp, *endcp, *shellname, *shellarg, *oldpnbuf;
        char **shellargp = NULL, **tmpsap;
        struct vnode *scriptvp;
        uid_t script_uid = -1;
@@ -103,6 +103,7 @@ exec_script_makecmds(struct proc *p, str
        for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen;
            cp++) {
                if (*cp == '\n') {
+                       endcp = cp;
                        *cp = '\0';
                        break;
                }
@@ -119,21 +120,23 @@ exec_script_makecmds(struct proc *p, str
            cp++)
                ;

+       /* return error when the shell name is not specified */
+       if (cp == endcp)
+               return ENOENT;
+
        /* collect the shell name; remember its length for later */
        shellname = cp;
        shellnamelen = 0;
-       if (*cp == '\0')
-               goto check_shell;
        for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++)
                shellnamelen++;
-       if (*cp == '\0')
+       if (cp == endcp)
                goto check_shell;
        *cp++ = '\0';

        /* skip spaces before any argument */
        for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++)
                ;
-       if (*cp == '\0')
+       if (cp == endcp)
                goto check_shell;

        /*
@@ -142,9 +145,7 @@ exec_script_makecmds(struct proc *p, str
         * behaviour.
         */
        shellarg = cp;
-       for ( /* cp = cp */ ; *cp != '\0'; cp++)
-               shellarglen++;
-       *cp++ = '\0';
+       shellarglen = endcp - cp;

 check_shell:
        /*