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Message-Id: <200909090907.n89975Fg042932@www.freebsd.org>
Date: Wed, 9 Sep 2009 09:07:05 GMT
From: Archer <n/a@FreeBSD.org>
To: freebsd-gnats-submit@FreeBSD.org
Subject: Kernel memory corruption, kernel panic as a result
X-Send-Pr-Version: www-3.1
X-GNATS-Notify:

>Number:         138657
>Category:       kern
>Synopsis:       [panic] [patch] Kernel memory corruption, ucred.cr_groups[] [regression]
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    brooks
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Sep 09 09:10:03 UTC 2009
>Closed-Date:    Thu Sep 24 21:46:10 UTC 2009
>Last-Modified:  Thu Sep 24 21:46:10 UTC 2009
>Originator:     Archer
>Release:        FreeBSD 8.0-BETA4
>Organization:
n/a
>Environment:
FreeBSD serv 8.0-BETA4 FreeBSD 8.0-BETA4 #1: Sat Sep 8 19:20:53 MSD 2009 root@serv:/usr/obj/usr/src/sys/MYKERN i386
>Description:
Lets take a look at this code in ufs_vnops.c file:
refcount_init(&ucred.cr_ref, 1);
ucred.cr_uid = ip->i_uid;
ucred.cr_ngroups = 1;
ucred.cr_groups[0] = dp->i_gid;<---problem here
ucp = &ucred;

ucred structure variable is used here. It's a local structure so it's allocated on stack. Now lets take a look at the structure definition:
struct ucred {
--skipped...
gid_t *cr_groups;
--skipped...
};

As we see we've got a pointer. But this pointer is not initialized at the point of usage. So it contains some arbitrary value from the stack. And then that memory gets overwritten. Lets take a look at the assembly listing:
mov edx, [esi+6Ch]
mov eax, [ebp+var_140]<---here we read some arbitrary pointer from the stack
mov [eax], edx<---and here we smash the data at our arbitrary pointer

In my case some memory around ufs_lookup was overwritten.
>How-To-Repeat:
Enable QUOTA and SUIDDIR at the kernel options, set them on some partition and try to create a directory there.
For me worked tar -xvjf phpMyAdmin-3.2.1-all-languages.tar.bz2 which also calls mkdir when extracting files.

>Fix:
In FreeBSD 7.1 ucred structure was defined with cr_groups array instead or pointer. So at some places in 8.0 version this was fixed by creating local gid_t and assigning it's address to the pointer. And some places (and described above is one of them was missed for unknown reason). 
I suppose we should allocate memory for our pointer before using it so recklessly. It's also possible to create a local gid_t and assigning it's address to the pointer (this is done a bit lower at ufs_vnops.c file). And I suggest to review the code that works with this pointer, the same mistake may happen elsewhere.

>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: freebsd-bugs->brooks 
Responsible-Changed-By: gavin 
Responsible-Changed-When: Wed Sep 9 12:30:06 UTC 2009 
Responsible-Changed-Why:  
Brooks, could you take a look at this please?  It appears to be fallout 
from the ucred changes.  THanks! 

http://www.freebsd.org/cgi/query-pr.cgi?pr=138657 

From: Brooks Davis <brooks@freebsd.org>
To: Archer <n/a@freebsd.org>
Cc: freebsd-gnats-submit@freebsd.org
Subject: Re: kern/138657: Kernel memory corruption, kernel panic as a result
Date: Wed, 9 Sep 2009 09:03:06 -0500

 Thanks for your report and detailed analysis.  I'm not sure how I
 handled the second instance of this in ufs_vnops.c and missed the first.
 Here's a patch that I believe should work around this.  Can you test it?
 
 I'd prefer we changed this code to have a credential with proper life
 cycle management even if we just create one at boot and hang it on a
 global variable, but adding extra storeage on the stack seemed less
 disruptive for the first cut.
 
 -- Brooks
 
 Index: ufs_vnops.c
 ===================================================================
 --- ufs_vnops.c	(revision 196736)
 +++ ufs_vnops.c	(working copy)
 @@ -1449,6 +1449,7 @@
  	{
  #ifdef QUOTA
  		struct ucred ucred, *ucp;
 +		gid_t ucred_group;
  		ucp = cnp->cn_cred;
  #endif
  		/*
 @@ -1476,6 +1477,7 @@
  				refcount_init(&ucred.cr_ref, 1);
  				ucred.cr_uid = ip->i_uid;
  				ucred.cr_ngroups = 1;
 +				ucred.cr_groups = &ucred_group;
  				ucred.cr_groups[0] = dp->i_gid;
  				ucp = &ucred;
  			}

Date: Wed, 09 Sep 2009 19:38:10 +0400
From: fghjfg hjfg <kjhmn3934f@inbox.ru>
Reply-To: fghjfg hjfg <kjhmn3934f@inbox.ru>
To: bug-followup@FreeBSD.org
Subject: Re: kern/138657: [panic] [patch] Kernel memory corruption, ucred.cr_groups[] [regression]

 Yup, this one worked just fine. Hope this bug won't happen elsewhere :) I guess this report can be closed.
 
 -- Archer
State-Changed-From-To: open->patched 
State-Changed-By: brooks 
State-Changed-When: Thu Sep 17 12:38:50 UTC 2009 
State-Changed-Why:  
Committed patch to HEAD.  Awaiting merge to 8. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=138657 

From: dfilter@FreeBSD.ORG (dfilter service)
To: bug-followup@FreeBSD.org
Cc:  
Subject: Re: kern/138657: commit references a PR
Date: Thu, 17 Sep 2009 12:35:27 +0000 (UTC)

 Author: brooks
 Date: Thu Sep 17 12:35:13 2009
 New Revision: 197269
 URL: http://svn.freebsd.org/changeset/base/197269
 
 Log:
   Allocate space for the group array in a static credential used in
   the quota code.  One case was correctly handled in r194498, but
   this one was missed.
   
   PR:		kern/138657
   Tested by:	PR submitter
   MFC after:	3 days
 
 Modified:
   head/sys/ufs/ufs/ufs_vnops.c
 
 Modified: head/sys/ufs/ufs/ufs_vnops.c
 ==============================================================================
 --- head/sys/ufs/ufs/ufs_vnops.c	Thu Sep 17 12:27:06 2009	(r197268)
 +++ head/sys/ufs/ufs/ufs_vnops.c	Thu Sep 17 12:35:13 2009	(r197269)
 @@ -1449,6 +1449,7 @@ ufs_mkdir(ap)
  	{
  #ifdef QUOTA
  		struct ucred ucred, *ucp;
 +		gid_t ucred_group;
  		ucp = cnp->cn_cred;
  #endif
  		/*
 @@ -1476,6 +1477,7 @@ ufs_mkdir(ap)
  				refcount_init(&ucred.cr_ref, 1);
  				ucred.cr_uid = ip->i_uid;
  				ucred.cr_ngroups = 1;
 +				ucred.cr_groups = &ucred_group;
  				ucred.cr_groups[0] = dp->i_gid;
  				ucp = &ucred;
  			}
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From: dfilter@FreeBSD.ORG (dfilter service)
To: bug-followup@FreeBSD.org
Cc:  
Subject: Re: kern/138657: commit references a PR
Date: Thu, 24 Sep 2009 21:33:07 +0000 (UTC)

 Author: brooks
 Date: Thu Sep 24 21:32:56 2009
 New Revision: 197473
 URL: http://svn.freebsd.org/changeset/base/197473
 
 Log:
   MFC r197269:
   Allocate space for the group array in a static credential used in
   the quota code.  One case was correctly handled in r194498, but
   this one was missed.
   
   PR:		kern/138657
   Tested by:	PR submitter
   MFC after:	3 days
   Approved by:	re@ (kib)
 
 Modified:
   stable/8/sys/   (props changed)
   stable/8/sys/amd64/include/xen/   (props changed)
   stable/8/sys/cddl/contrib/opensolaris/   (props changed)
   stable/8/sys/contrib/dev/acpica/   (props changed)
   stable/8/sys/contrib/pf/   (props changed)
   stable/8/sys/dev/xen/xenpci/   (props changed)
   stable/8/sys/ufs/ufs/ufs_vnops.c
 
 Modified: stable/8/sys/ufs/ufs/ufs_vnops.c
 ==============================================================================
 --- stable/8/sys/ufs/ufs/ufs_vnops.c	Thu Sep 24 20:43:08 2009	(r197472)
 +++ stable/8/sys/ufs/ufs/ufs_vnops.c	Thu Sep 24 21:32:56 2009	(r197473)
 @@ -1449,6 +1449,7 @@ ufs_mkdir(ap)
  	{
  #ifdef QUOTA
  		struct ucred ucred, *ucp;
 +		gid_t ucred_group;
  		ucp = cnp->cn_cred;
  #endif
  		/*
 @@ -1476,6 +1477,7 @@ ufs_mkdir(ap)
  				refcount_init(&ucred.cr_ref, 1);
  				ucred.cr_uid = ip->i_uid;
  				ucred.cr_ngroups = 1;
 +				ucred.cr_groups = &ucred_group;
  				ucred.cr_groups[0] = dp->i_gid;
  				ucp = &ucred;
  			}
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State-Changed-From-To: patched->closed 
State-Changed-By: brooks 
State-Changed-When: Thu Sep 24 21:44:49 UTC 2009 
State-Changed-Why:  
Merged to 8 

http://www.freebsd.org/cgi/query-pr.cgi?pr=138657 
>Unformatted:
