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xen-gnt: prevent adding duplicate gnt callbacks
With the current implementation, the callback in the tail of the list can be added twice, because the check done in gnttab_request_free_callback is bogus, callback->next can be NULL if it is the last callback in the list. If we add the same callback twice we end up with an infinite loop, were callback == callback->next. Replace this check with a proper one that iterates over the list to see if the callback has already been added. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Acked-by: Matt Wilson <msw@amazon.com> Reviewed-by: David Vrabel <david.vrabel@citrix.com> CC: stable@vger.kernel.org
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@ -730,9 +730,18 @@ void gnttab_request_free_callback(struct gnttab_free_callback *callback,
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void (*fn)(void *), void *arg, u16 count)
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{
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unsigned long flags;
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struct gnttab_free_callback *cb;
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spin_lock_irqsave(&gnttab_list_lock, flags);
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if (callback->next)
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/* Check if the callback is already on the list */
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cb = gnttab_free_callback_list;
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while (cb) {
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if (cb == callback)
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goto out;
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cb = cb->next;
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}
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callback->fn = fn;
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callback->arg = arg;
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callback->count = count;
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