kern/118153: [fix] "semprt" can be invalid after wakeup in the
semop()
Ivan Shcheklein
shcheklein at gmail.com
Tue Nov 20 08:30:02 PST 2007
>Number: 118153
>Category: kern
>Synopsis: [fix] "semprt" can be invalid after wakeup in the semop()
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Nov 20 16:30:01 UTC 2007
>Closed-Date:
>Last-Modified:
>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 buf 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:
>Unformatted:
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