NetBSD Problem Report #57229

From buhrow@nfbcal.org  Mon Feb 13 17:15:24 2023
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Message-Id: <202302131715.31DHFKFY006240@nfbcal.org>
Date: Mon, 13 Feb 2023 09:15:21 -0800 (PST)
From: buhrow@nfbcal.org
Reply-To: buhrow@nfbcal.org
To: gnats-bugs@NetBSD.org
Subject: Fix for devsw_attach
X-Send-Pr-Version: 3.95

>Number:         57229
>Category:       kern
>Synopsis:       Fix for devsw_attach
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    buhrow
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 13 17:20:00 +0000 2023
>Closed-Date:    Tue Feb 14 17:25:27 +0000 2023
>Last-Modified:  Tue Feb 14 17:25:27 +0000 2023
>Originator:     Brian Buhrow
>Release:        
>Organization:
	NFB of California
>Environment:


System: NetBSD loth-9.nfbcal.org 9.99.77 NetBSD 9.99.77 (XEN3_DOMU) #0: Wed Jan 13 02:37:15 PST 2021  buhrow@loth-9.nfbcal.org:/usr/local/netbsd/obj-current/sys/arch/amd64/compile/XEN3_DOMU amd64
>Description:

	When a device driver calls devsw_attach() it has the option of attaching a block device
structure and a character device structure, or, just the character device structure.
With the existing code, if a driver elects not to attach a block device structure and if it
asks for a major number to be dynamically assigned to its character interface, 
that driver will not be able to detach and reattach its character driver interface.  This is a very 
long standing bug which didn't come to light until we began using loadable kernel modules more
heavily.  this patch fixes this problem.  With this patch in place, drivers that implement only
a character device interface may detach and reattach that character interface as often as they
like.
>How-To-Repeat:

Try to load a kernel module that implements only a character driver interface, unload it and
then try to load it again.  It will not load because devsw_attach() wil return EINVAL.
>Fix:


Index: subr_devsw.c
===================================================================
RCS file: /cvsroot/src/sys/kern/subr_devsw.c,v
retrieving revision 1.49
diff -u -r1.49 subr_devsw.c
--- subr_devsw.c	29 Oct 2022 10:52:36 -0000	1.49
+++ subr_devsw.c	13 Feb 2023 17:03:04 -0000
@@ -1,4 +1,4 @@
-/*	$NetBSD$	*/
+/*	$NetBSD: subr_devsw.c,v 1.49 2022/10/29 10:52:36 riastradh Exp $	*/

 /*-
  * Copyright (c) 2001, 2002, 2007, 2008 The NetBSD Foundation, Inc.
@@ -69,7 +69,7 @@
  */

 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD$");
+__KERNEL_RCSID(0, "$NetBSD: subr_devsw.c,v 1.49 2022/10/29 10:52:36 riastradh Exp $");

 #ifdef _KERNEL_OPT
 #include "opt_dtrace.h"
@@ -397,7 +397,7 @@
 		if (conv->d_name == NULL || strcmp(devname, conv->d_name) != 0)
 			continue;

-		if (*bmajor < 0)
+		if ((bdev != NULL) && (*bmajor < 0)) 
 			*bmajor = conv->d_bmajor;
 		if (*cmajor < 0)
 			*cmajor = conv->d_cmajor;

>Release-Note:

>Audit-Trail:

Responsible-Changed-From-To: gnats-admin->buhrow
Responsible-Changed-By: buhrow@NetBSD.org
Responsible-Changed-When: Mon, 13 Feb 2023 18:55:47 +0000
Responsible-Changed-Why:
Brian will shepherd this bug to closure.


From: "Brian Buhrow" <buhrow@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/57229 CVS commit: src/sys/kern
Date: Mon, 13 Feb 2023 19:07:14 +0000

 Module Name:	src
 Committed By:	buhrow
 Date:		Mon Feb 13 19:07:14 UTC 2023

 Modified Files:
 	src/sys/kern: subr_devsw.c

 Log Message:
 	When a device driver calls devsw_attach() it has the option of attaching a block device
 structure and a character device structure, or, just the character device structure.
 With the existing code, if a driver elects not to attach a block device structure and if it
 asks for a major number to be dynamically assigned to its character interface,
 that driver will not be able to detach and reattach its character driver interface.  This is a very
 long standing bug which didn't come to light until we began using loadable kernel modules more
 heavily.  this patch fixes this problem.  With this patch in place, drivers that implement only
 a character device interface may detach and reattach that character interface as often as they
 need to.

 Fixes PR kern/57229


 To generate a diff of this commit:
 cvs rdiff -u -r1.49 -r1.50 src/sys/kern/subr_devsw.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->pending-pullups
State-Changed-By: buhrow@NetBSD.org
State-Changed-When: Tue, 14 Feb 2023 00:20:06 +0000
State-Changed-Why:
Requested pullup-9#1595 and pullup-10#84


From: "Martin Husemann" <martin@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/57229 CVS commit: [netbsd-10] src/sys/kern
Date: Tue, 14 Feb 2023 16:16:30 +0000

 Module Name:	src
 Committed By:	martin
 Date:		Tue Feb 14 16:16:30 UTC 2023

 Modified Files:
 	src/sys/kern [netbsd-10]: subr_devsw.c

 Log Message:
 Pull up following revision(s) (requested by buhrow in ticket #84):

 	sys/kern/subr_devsw.c: revision 1.50

         When a device driver calls devsw_attach() it has the option of attaching a block device
 structure and a character device structure, or, just the character device structure.
 With the existing code, if a driver elects not to attach a block device structure and if it
 asks for a major number to be dynamically assigned to its character interface,
 that driver will not be able to detach and reattach its character driver interface.  This is a very
 long standing bug which didn't come to light until we began using loadable kernel modules more
 heavily.  this patch fixes this problem.  With this patch in place, drivers that implement only
 a character device interface may detach and reattach that character interface as often as they
 need to.

 Fixes PR kern/57229


 To generate a diff of this commit:
 cvs rdiff -u -r1.49 -r1.49.2.1 src/sys/kern/subr_devsw.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

From: "Martin Husemann" <martin@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/57229 CVS commit: [netbsd-9] src/sys/kern
Date: Tue, 14 Feb 2023 16:19:00 +0000

 Module Name:	src
 Committed By:	martin
 Date:		Tue Feb 14 16:19:00 UTC 2023

 Modified Files:
 	src/sys/kern [netbsd-9]: subr_devsw.c

 Log Message:
 Pull up following revision(s) (requested by buhrow in ticket #1595):

 	sys/kern/subr_devsw.c: revision 1.50

         When a device driver calls devsw_attach() it has the option of attaching a block device
 structure and a character device structure, or, just the character device structure.
 With the existing code, if a driver elects not to attach a block device structure and if it
 asks for a major number to be dynamically assigned to its character interface,
 that driver will not be able to detach and reattach its character driver interface.  This is a very
 long standing bug which didn't come to light until we began using loadable kernel modules more
 heavily.  this patch fixes this problem.  With this patch in place, drivers that implement only
 a character device interface may detach and reattach that character interface as often as they
 need to.

 Fixes PR kern/57229


 To generate a diff of this commit:
 cvs rdiff -u -r1.38 -r1.38.8.1 src/sys/kern/subr_devsw.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: pending-pullups->closed
State-Changed-By: buhrow@NetBSD.org
State-Changed-When: Tue, 14 Feb 2023 17:25:27 +0000
State-Changed-Why:
Pullups committed.


>Unformatted:
 Confidential:	no
 Devsw_attach, when called with character interfaces only, prevents detaching and reattaching.
 Severity: serious
 Priority: medium
 Category: kern
 Class: sw-bug
 Release:	NetBSD 9.99.77, but applies to many versions of NetBSD
 	<Please check that the above is correct for the bug being reported,>
 	<and append source date of snapshot, if applicable (one line).>

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