From https://ftp.gnu.org/gnu/bash/bash-5.0-patches/bash50-016

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>

			     BASH PATCH REPORT
			     =================

Bash-Release:	5.0
Patch-ID:	bash50-016

Bug-Reported-by:	sunnycemetery@gmail.com
Bug-Reference-ID:	<20190316041534.GB22884@midnight>
Bug-Reference-URL:	https://lists.gnu.org/archive/html/bug-bash/2019-03/msg00070.html

Bug-Description:

Bash waits too long to reap /dev/fd process substitutions used as redirections
with loops and group commands, which can lead to file descriptor exhaustion.

Patch (apply with `patch -p0'):

*** ../bash-5.0-patched/execute_cmd.c	2019-04-19 15:46:36.000000000 -0400
--- b/execute_cmd.c	2019-07-01 16:45:49.000000000 -0400
***************
*** 1104,1107 ****
--- 1085,1104 ----
        discard_unwind_frame ("internal_fifos");
      }
+ # if defined (HAVE_DEV_FD)
+   /* Reap process substitutions at the end of loops */
+   switch (command->type)
+     {
+     case cm_while:
+     case cm_until:
+     case cm_for:
+     case cm_group:
+ #    if defined (ARITH_FOR_COMMAND)
+     case cm_arith_for:
+ #    endif
+       reap_procsubs ();
+     default:
+       break;
+     }
+ #  endif /* HAVE_DEV_FD */
  #endif
  

*** ../bash-5.0/patchlevel.h	2016-06-22 14:51:03.000000000 -0400
--- b/patchlevel.h	2016-10-01 11:01:28.000000000 -0400
***************
*** 26,30 ****
     looks for to find the patch level (for the sccs version string). */
  
! #define PATCHLEVEL 15
  
  #endif /* _PATCHLEVEL_H_ */
--- 26,30 ----
     looks for to find the patch level (for the sccs version string). */
  
! #define PATCHLEVEL 16
  
  #endif /* _PATCHLEVEL_H_ */