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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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