lockd: fix race in nlm_release()
The sm_count is decremented to zero but left on the nsm_handles list. So in the space between decrementing sm_count and acquiring nsm_mutex, it is possible for another task to find this nsm_handle, increment the use count and then enter nsm_release itself. Thus there's nothing to prevent the nsm being freed before we acquire nsm_mutex here. Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
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@ -529,12 +529,10 @@ nsm_release(struct nsm_handle *nsm)
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{
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{
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if (!nsm)
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if (!nsm)
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return;
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return;
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mutex_lock(&nsm_mutex);
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if (atomic_dec_and_test(&nsm->sm_count)) {
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if (atomic_dec_and_test(&nsm->sm_count)) {
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mutex_lock(&nsm_mutex);
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list_del(&nsm->sm_link);
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if (atomic_read(&nsm->sm_count) == 0) {
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kfree(nsm);
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list_del(&nsm->sm_link);
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kfree(nsm);
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}
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mutex_unlock(&nsm_mutex);
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}
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}
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mutex_unlock(&nsm_mutex);
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}
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}
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