msh: fix obscure case with backticks and closed fd 1

1 files changed, 12 insertions, 7 deletions

diff --git a/shell/msh.c b/shell/msh.c
index 4feede6fa..ac49af14c 100644
--- a/shell/msh.c
+++ b/shell/msh.c
@@ -2546,7 +2546,7 @@ static int execute(struct op *t, int *pin, int *pout, int act)
                                 interactive = 0;
                                 if (pin == NULL) {
                                         close(0);
-                                        open(bb_dev_null, O_RDONLY);
+                                        xopen(bb_dev_null, O_RDONLY);
                                 }
                                 _exit(execute(t->left, pin, pout, FEXEC));
                         }
@@ -2823,12 +2823,12 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
 #endif
 
         if (pin != NULL) {
-                dup2(pin[0], 0);
-                closepipe(pin);
+                xmove_fd(pin[0], 0);
+                if (pin[1] != 0) close(pin[1]);
         }
         if (pout != NULL) {
-                dup2(pout[1], 1);
-                closepipe(pout);
+                xmove_fd(pout[1], 1);
+                if (pout[1] != 1) close(pout[0]);
         }
 
         iopp = t->ioact;
@@ -4166,8 +4166,13 @@ static int grave(int quoted)
                 if (ourtrap[j] && signal(j, SIG_IGN) != SIG_IGN)
                         signal(j, SIG_DFL);
 
-        dup2(pf[1], 1);
-        closepipe(pf);
+        /* Testcase where below checks are needed:
+         * close stdout & run this script:
+         *  files=`ls`
+         *  echo "$files" >zz
+         */
+        xmove_fd(pf[1], 1);
+        if (pf[0] != 1) close(pf[0]);
 
         argument_list[0] = (char *) DEFAULT_SHELL;
         argument_list[1] = (char *) "-c";