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Re: coproc and existing variables


From: Grisha Levit
Subject: Re: coproc and existing variables
Date: Mon, 23 May 2016 12:45:39 -0400

On Thu, May 19, 2016 at 11:05 AM, Chet Ramey <address@hidden> wrote:

>       * The %s_PID variable is unbound unconditionally
>
> BTW, this is exploitable for unsetting read-only variables.

Same change as for getopts.

This should probably instead be the same change as was previously done for unsetting the FD array variable, i.e.:

diff --git a/execute_cmd.c b/execute_cmd.c
index 09f4772..e9a0b9d 100644
--- a/execute_cmd.c
+++ b/execute_cmd.c
@@ -2239,7 +2239,7 @@ coproc_unsetvars (cp)
   namevar = xmalloc (l + 16);

   sprintf (namevar, "%s_PID", cp->c_name);
-  unbind_variable_noref (namevar);
+  check_unbind_variable (namevar);

 #if defined (ARRAY_VARS)
   check_unbind_variable (cp->c_name);

Otherwise the wrong thing gets unset:

$ declare -n ref_PID=var; coproc ref { :; }; wait; declare -p ref_PID var
[1] 50943
[1]+  Done                    coproc ref { :; }
bash: declare: ref_PID: not found
declare -- var="50943"

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