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Date: Sat, 7 Nov 1998 21:59:35 -0800 (PST)
From: marcs@znep.com
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To: FreeBSD-gnats-submit@FreeBSD.ORG
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Subject: kern/8599: poll(2) sets POLLNVAL for negative descriptors
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>Number:         8599
>Category:       kern
>Synopsis:       poll(2) sets POLLNVAL for negative descriptors
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:
>Keywords:
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Nov  7 22:10:00 PST 1998
>Last-Modified:
>Originator:     Marc Slemko
>Organization:
>Release:        FreeBSD 3.0-CURRENT i386
>Environment:


FreeBSD alive.znep.com 3.0-CURRENT FreeBSD 3.0-CURRENT #8: Sat Nov  7 21:26:59 PST 1998     marcs@alive.znep.com:/usr/src/sys/compile/ALIVE  i386

3.0-current as of a few days ago.

>Description:

poll(2) sets POLLNVAL for descriptors passed in that are less than
0.  This makes it difficult to do efficient manipulation of the 
struct pollfd since you can't leave a slot empty.

>How-To-Repeat:

Set fds[n].fd = -1 and do a poll on it.  It treats it as an 
POLLNVAL when it should ignore it.

>Fix:

I have no idea why fds->fd was being cast to a u_int.

Index: sys_generic.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/sys_generic.c,v
retrieving revision 1.41
diff -u -r1.41 sys_generic.c
--- sys_generic.c	1998/09/05 14:30:11	1.41
+++ sys_generic.c	1998/11/08 05:26:43
@@ -793,9 +793,11 @@
 	int n = 0;
 
 	for (i = 0; i < nfd; i++, fds++) {
-		if ((u_int)fds->fd >= fdp->fd_nfiles) {
+		if (fds->fd >= fdp->fd_nfiles) {
 			fds->revents = POLLNVAL;
 			n++;
+		} else if (fds->fd < 0) {
+			fds->revents = 0;
 		} else {
 			fp = fdp->fd_ofiles[fds->fd];
 			if (fp == 0) {
>Audit-Trail:
>Unformatted:

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