[9front] [PATCH] kernel: disallow executing from #| or #d

[Jacob Moody <moody@mail.posixcafe.org>]

Hello,

I noticed that you could execute from #| and #d.
ex:

cpu% bind '#|' /n/pipetest
cpu% /n/pipetest/data1 &
cpu% echo '#!/bin/rc' >> /n/pipetest/data
cpu% echo 'echo hello' >> /n/pipetest/data
cpu% hello

I believe this would also work for binaries
if the writer could predict what parts of the binary
the kernel will want to read. I am inclined to
block this behavior but would be curious what others
think. Included is a patch to error on OEXEC opens
in devdup and devpipe.

thanks,
moody

---
diff 6ca8e6bbafcc871301a90aa7bd4ca10533b1999a 521f304f5db4c74740b3e00503e2bf22e9f60dc6
--- a/sys/src/9/port/devdup.c	Mon May  9 11:22:00 2022
+++ b/sys/src/9/port/devdup.c	Tue May 10 00:35:16 2022
@@ -63,7 +63,7 @@
 	Chan *f;
 	int fd, twicefd;

-	if(omode & ORCLOSE)
+	if(omode & ORCLOSE || omode & OEXEC)
 		error(Eperm);
 	if(c->qid.type & QTDIR){
 		if(omode != 0)
--- a/sys/src/9/port/devpipe.c	Mon May  9 11:22:00 2022
+++ b/sys/src/9/port/devpipe.c	Tue May 10 00:35:16 2022
@@ -228,6 +228,8 @@
 		c->offset = 0;
 		return c;
 	}
+	if(omode == OEXEC)
+		error(Eperm);

 	p = c->aux;
 	qlock(p);