hush: handle empty execs

Sometimes variable expansions yield empty strings, and if they happen to
be a command someone wants to run like `$foo`, then hush currently
segfaults.  So handle `` and $().

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/shell/hush.c b/shell/hush.c
index 2d333d731..1d2826d9a 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -3895,6 +3895,12 @@ static NOINLINE int run_pipe(struct pipe *pi)
                         argv_expanded = expand_strvec_to_strvec(argv + command->assignment_cnt);
                 }
 
+                /* if someone gives us an empty string: ``, $(), ... */
+                if (!argv_expanded[0]) {
+                        debug_leave();
+                        return 0;
+                }
+
                 x = find_builtin(argv_expanded[0]);
 #if ENABLE_HUSH_FUNCTIONS
                 funcp = NULL;