ash: eval: Reap zombies after built-in commands and functions

Upstream commit:

    Date: Mon, 26 Mar 2018 23:55:50 +0800
    eval: Reap zombies after built-in commands and functions

    Currently dash does not reap dead children after built-in commands
    or functions.  This means that if you construct a loop consisting
    of solely built-in commands and functions, then zombies can hang
    around indefinitely.

    This patch fixes this by reaping when necessary after each built-in
    command and function.

    Reported-by: Denys Vlasenko <vda.linux@googlemail.com>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

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

1 files changed, 10 insertions, 16 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 389db3cd0..8047cf98f 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -5355,10 +5355,10 @@ waitforjob(struct job *jp)
 {
         int st;
 
-        TRACE(("waitforjob(%%%d) called\n", jobno(jp)));
+        TRACE(("waitforjob(%%%d) called\n", jp ? jobno(jp) : 0));
 
         INT_OFF;
-        while (jp->state == JOBRUNNING) {
+        while ((jp && jp->state == JOBRUNNING) || got_sigchld) {
                 /* In non-interactive shells, we _can_ get
                  * a keyboard signal here and be EINTRed,
                  * but we just loop back, waiting for command to complete.
@@ -5393,6 +5393,8 @@ waitforjob(struct job *jp)
         }
         INT_ON;
 
+        if (!jp)
+                return exitstatus;
         st = getstatus(jp);
 #if JOBS
         if (jp->jobctl) {
@@ -10311,6 +10313,8 @@ evalcommand(union node *cmd, int flags)
                 goto out;
         }
 
+        jp = NULL;
+
         /* Execute the command. */
         switch (cmdentry.cmdtype) {
         default: {
@@ -10365,7 +10369,6 @@ evalcommand(union node *cmd, int flags)
                         jp = makejob(/*cmd,*/ 1);
                         if (forkshell(jp, cmd, FORK_FG) != 0) {
                                 /* parent */
-                                status = waitforjob(jp);
                                 INT_ON;
                                 TRACE(("forked child exited with %d\n", status));
                                 break;
@@ -10384,33 +10387,24 @@ evalcommand(union node *cmd, int flags)
                         if (cmd_is_exec && argc > 1)
                                 listsetvar(varlist.list, VEXPORT);
                 }
-
-                /* Tight loop with builtins only:
-                 * "while kill -0 $child; do true; done"
-                 * will never exit even if $child died, unless we do this
-                 * to reap the zombie and make kill detect that it's gone: */
-                dowait(DOWAIT_NONBLOCK, NULL);
-
                 if (evalbltin(cmdentry.u.cmd, argc, argv, flags)) {
                         if (exception_type == EXERROR && spclbltin <= 0) {
                                 FORCE_INT_ON;
-                                goto readstatus;
+                                break;
                         }
  raise:
                         longjmp(exception_handler->loc, 1);
                 }
-                goto readstatus;
+                break;
 
         case CMDFUNCTION:
-                /* See above for the rationale */
-                dowait(DOWAIT_NONBLOCK, NULL);
                 if (evalfun(cmdentry.u.func, argc, argv, flags))
                         goto raise;
- readstatus:
-                status = exitstatus;
                 break;
         } /* switch */
 
+        status = waitforjob(jp);
+
  out:
         if (cmd->ncmd.redirect)
                 popredir(/*drop:*/ cmd_is_exec);