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SubjectRe: [PATCH] ibmasm driver: don't use previously freed pointer
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On Fri, 2006-02-03 at 22:02, Greg KH wrote:
> On Fri, Feb 03, 2006 at 02:26:38PM -0800, Max Asbock wrote:
> > ibmasm driver:
> > Fix the command_put() function which uses a pointer for a spinlock that
> > can be freed before dereferencing it.
> >
> > Signed-off-by: Max Asbock masbock@us.ibm.com
> >
> > ---
> >
> > diff -burpN linux-2.6.16-rc1/drivers/misc/ibmasm/ibmasm.h linux-2.6.16-rc1.ibmasm/drivers/misc/ibmasm/ibmasm.h
> > --- linux-2.6.16-rc1/drivers/misc/ibmasm/ibmasm.h 2006-02-01 11:50:01.000000000 -0800
> > +++ linux-2.6.16-rc1.ibmasm/drivers/misc/ibmasm/ibmasm.h 2006-02-03 13:57:42.000000000 -0800
> > @@ -101,10 +101,11 @@ struct command {
> > static inline void command_put(struct command *cmd)
> > {
> > unsigned long flags;
> > + spinlock_t *lock = cmd->lock;
> >
> > - spin_lock_irqsave(cmd->lock, flags);
> > + spin_lock_irqsave(lock, flags);
> > kobject_put(&cmd->kobj);
> > - spin_unlock_irqrestore(cmd->lock, flags);
> > + spin_unlock_irqrestore(lock, flags);
> > }
>
> If this patch is true, doesn't the spinlock the pointer is pointing out
> still get deleted?
>
> Yes you save a pointer off, but it looks like the problem is still
> present.
>
> Or am I missing something?
>

The lock pointer in struct command points to a spinlock outside the
structure that doesn't get deleted.

max

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