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Date: Tue, 15 Mar 2005 18:22:30 GMT
From: LiangYi <liangyi571@hotmail.com>
To: freebsd-gnats-submit@FreeBSD.org
Subject: Fast forward will carsh the system in 5.x.
X-Send-Pr-Version: www-2.3

>Number:         78893
>Category:       kern
>Synopsis:       [patch] ip_fastfwd.c: fast forward will crash the system in 5.x.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    glebius
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Mar 15 18:30:02 GMT 2005
>Closed-Date:    Mon Apr 04 11:04:48 GMT 2005
>Last-Modified:  Mon Apr 04 11:04:48 GMT 2005
>Originator:     LiangYi
>Release:        5.3
>Organization:
lingzhou network Inc
>Environment:
FreeBSD 5.3-RELEASE
>Description:
      It seems there is a bug in ip_fastfwd.c which will crash the system when it runs in fast forward mode occasionally. The crash enviroment will like this: 
      net.inet.ip.fastforwarding = 1
      Do a over MTU ping on a busy interface 
>How-To-Repeat:
      same as above.
>Fix:
      Look at ip_fastfwd.c, function ip_fastforward, line 499. if_output will free the mbuf when it is failed. So if an error is occured 'm' will be freed, and the loop will break. Current code will free m twice which will crash the system later.
      Fix:
      update line 586 from: 
         "for (; m; m = m0) {"
      to
         "for (; m = m0; ) {"


>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: freebsd-bugs->andre 
Responsible-Changed-By: glebius 
Responsible-Changed-When: Thu Mar 17 20:16:46 GMT 2005 
Responsible-Changed-Why:  
Good catch, thanks! Your patch is correct, but I'd better don't 
use assignment as boolean expression.  I suggest this patch: 

diff -u -r1.26 ip_fastfwd.c 
--- ip_fastfwd.c        7 Jan 2005 01:45:44 -0000       1.26 
+++ ip_fastfwd.c        17 Mar 2005 20:13:52 -0000 
@@ -594,9 +594,8 @@ 
} while ((m = m0) != NULL); 
if (error) { 
/* Reclaim remaining fragments */ 
-                               for (; m; m = m0) { 
+                               for (m = m0; m; m = m0) { 
m0 = m->m_nextpkt; 
-                                       m->m_nextpkt = NULL; 
m_freem(m); 
} 
} else 


I think it is more clear. It also removes redundant assignment. 

I pass the PR and patch for Andre review, who is author of this file. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=78893 
Responsible-Changed-From-To: andre->glebius 
Responsible-Changed-By: glebius 
Responsible-Changed-When: Tue Mar 29 13:43:31 GMT 2005 
Responsible-Changed-Why:  
Grab this one. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=78893 
State-Changed-From-To: open->patched 
State-Changed-By: glebius 
State-Changed-When: Tue Mar 29 13:44:04 GMT 2005 
State-Changed-Why:  
Committed to HEAD, thanks! 

http://www.freebsd.org/cgi/query-pr.cgi?pr=78893 
State-Changed-From-To: patched->closed 
State-Changed-By: glebius 
State-Changed-When: Mon Apr 4 11:04:30 GMT 2005 
State-Changed-Why:  
Merged to RELENG_5. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=78893 
>Unformatted:
