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Date: Tue, 20 Nov 2007 16:22:53 GMT
From: Ivan Shcheklein <shcheklein@gmail.com>
To: freebsd-gnats-submit@FreeBSD.org
Subject: [fix] "semprt" can be invalid after wakeup in the semop()
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>Number:         118153
>Category:       kern
>Synopsis:       [sysvshm] [patch] "semprt" can be invalid after wakeup in the semop()
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    gavin
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Nov 20 16:30:01 UTC 2007
>Closed-Date:    Fri May 16 14:19:33 UTC 2008
>Last-Modified:  Fri May 16 14:19:33 UTC 2008
>Originator:     Ivan Shcheklein
>Release:        FREEBSD-6.2
>Organization:
ISP RAS
>Environment:
FreeBSD 6.2-RELEASE i386
>Description:
Fistly, sorry for the my previous post of this bug:
http://lists.freebsd.org/pipermail/freebsd-bugs/2007-November/026847.html

I didn't know about the better way to submit bugs. I think, it can be
removed or marked as duplicate to this one.

The bug itself is the following.

In sysv_sem.c::1173 we have:

                /* ... semaphores wakes up ... */
		
                if (sopptr->sem_op == 0)
			semptr->semzcnt--;
		else
			semptr->semncnt--;

Used here "semptr" after wakeup can be invalid due to "semakptr->u.sem_base"
can be changed during semaphore sleeping. (For example it can be changed by
removing another semaphore).

>How-To-Repeat:


>Fix:
The solution for this problem is quiet obvious. We must use "semakptr" to
get new "semptr". For example (possibly it can be written better):

                if (sopptr->sem_op == 0)
			(&semakptr->u.sem_base[sopptr->sem_num])->semzcnt--;
		else
			(&semakptr->u.sem_base[sopptr->sem_num])->semncnt--;

>Release-Note:
>Audit-Trail:
State-Changed-From-To: open->closed 
State-Changed-By: gavin 
State-Changed-When: Fri May 16 14:18:29 UTC 2008 
State-Changed-Why:  
Close, submitter has submitted another PR, kern/123731, with more details. 


Responsible-Changed-From-To: freebsd-bugs->gavin 
Responsible-Changed-By: gavin 
Responsible-Changed-When: Fri May 16 14:18:29 UTC 2008 
Responsible-Changed-Why:  
Track 

http://www.freebsd.org/cgi/query-pr.cgi?pr=118153 
>Unformatted:
