[PATCH] eval: avoid leaking memory associated with redirections

[Ron Yorston]

The following constructs result in ever-increasing memory usage:

   while true; do { true; } </dev/null; done
   while true; do ( true; ) </dev/null; done

For comparison, bash displays static memory usage in both cases.

This issue was reported for BusyBox ash which is derived from dash:

   https://bugs.busybox.net/show_bug.cgi?id=7748

Signed-off-by: Ron Yorston <r...@frippery.org>
---
 src/eval.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/eval.c b/src/eval.c
index 546ee1b..9f117ea 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -202,6 +202,7 @@ evaltree(union node *n, int flags)
        int (*evalfn)(union node *, int);
        unsigned isor;
        int status = 0;
+       struct stackmark smark;
        if (n == NULL) {
                TRACE(("evaltree(NULL) called\n"));
                goto out;
@@ -227,6 +228,7 @@ evaltree(union node *n, int flags)
                status = !evaltree(n->nnot.com, EV_TESTED);
                goto setstatus;
        case NREDIR:
+               setstackmark(&smark);
                errlinno = lineno = n->nredir.linno;
                if (funcline)
                        lineno -= funcline - 1;
@@ -236,6 +238,7 @@ evaltree(union node *n, int flags)
                         evaltree(n->nredir.n, flags & EV_TESTED);
                if (n->nredir.redirect)
                        popredir(0);
+               popstackmark(&smark);
                goto setstatus;
        case NCMD:
 #ifdef notyet
@@ -476,11 +479,13 @@ evalsubshell(union node *n, int flags)
        struct job *jp;
        int backgnd = (n->type == NBACKGND);
        int status;
+       struct stackmark smark;
 
        errlinno = lineno = n->nredir.linno;
        if (funcline)
                lineno -= funcline - 1;
 
+       setstackmark(&smark);
        expredir(n->nredir.redirect);
        if (!backgnd && flags & EV_EXIT && !have_traps())
                goto nofork;
@@ -500,6 +505,7 @@ nofork:
        if (! backgnd)
                status = waitforjob(jp);
        INTON;
+       popstackmark(&smark);
        return status;
 }
 
-- 
2.19.1