ash: fix local PATH assignments

The previous commit included code to use PATH values assigned to
local variables:

   PATH=/new/path:$PATH new_binary

It didn't work in the case when no fork was needed, for example:

   (PATH=/new/path:$PATH new_binary)

because the call to listsetvar() freed the PATH value that was
passed to shellexec().  The forking case only worked because the
spawn_forkshell() mechanism in busybox-w32 didn't allow the PATH
value to be freed.

Rewrite the code so it works whether or not a fork is needed.  The
code would also work on POSIX systems.

A cleaner solution could be extracted from dash commit cbb71a8
'eval: Add assignment built-in support again' but neither that nor
the current patch are suitable for submission to upstream BusyBox.
This one is preferred because it requires fewer changes from
upstream.

1 files changed, 20 insertions, 7 deletions

diff --git a/shell/ash.c b/shell/ash.c
index a659fd703..5195a8557 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -10531,6 +10531,9 @@ evalcommand(union node *cmd, int flags)
         int status;
         char **nargv;
         smallint cmd_is_exec;
+#if ENABLE_PLATFORM_MINGW32
+        int cmdpath;
+#endif
 
         errlinno = lineno = cmd->ncmd.linno;
         if (funcline)
@@ -10599,6 +10602,7 @@ evalcommand(union node *cmd, int flags)
         }
         status = redirectsafe(cmd->ncmd.redirect, REDIR_PUSH | REDIR_SAVEFD2);
 
+#if !ENABLE_PLATFORM_MINGW32
         path = vpath.var_text;
         for (argp = cmd->ncmd.assign; argp; argp = argp->narg.next) {
                 struct strlist **spp;
@@ -10615,14 +10619,17 @@ evalcommand(union node *cmd, int flags)
                  */
                 p = (*spp)->text;
                 if (varcmp(p, path) == 0)
-#if !ENABLE_PLATFORM_MINGW32
                         path = p;
+        }
 #else
-                        /* fix_pathvar may have modified the value of the local
-                         * variable so we look it up again */
-                        path = vpath.var_text;
-#endif
+        /* Set path after any local PATH= has been processed. */
+        for (argp = cmd->ncmd.assign; argp; argp = argp->narg.next) {
+                struct strlist **spp = varlist.lastp;
+                expandarg(argp, &varlist, EXP_VARTILDE);
+                mklocal((*spp)->text);
         }
+        path = vpath.var_text;
+#endif
 
         /* Print the command if xflag is set. */
         if (xflag) {
@@ -10780,7 +10787,13 @@ evalcommand(union node *cmd, int flags)
                         TRACE(("forked child exited with %d\n", status));
                         break;
                 }
-                /* goes through to shellexec() */
+                /* If we're running 'command -p' we need to use the value stored
+                 * in path by parse_command_args().  If PATH is a local variable
+                 * listsetvar() will free the value currently in path so we need
+                 * to fetch the updated version. */
+                cmdpath = (path != pathval());
+                listsetvar(varlist.list, VEXPORT|VSTACK);
+                shellexec(argv[0], argv, cmdpath ? path : pathval(), cmdentry.u.index);
 #else
                 if (!(flags & EV_EXIT) || may_have_traps) {
                         /* No, forking off a child is necessary */
@@ -10798,9 +10811,9 @@ evalcommand(union node *cmd, int flags)
                         FORCE_INT_ON;
                         /* fall through to exec'ing external program */
                 }
-#endif
                 listsetvar(varlist.list, VEXPORT|VSTACK);
                 shellexec(argv[0], argv, path, cmdentry.u.index);
+#endif
                 /* NOTREACHED */
         } /* default */
         case CMDBUILTIN: