Commit 164f98ad authored Feb 20, 2008 by J. Bruce Fields

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>

parent dd35210e

fs/lockd/host.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -529,12 +529,10 @@ nsm_release(struct nsm_handle *nsm)
		{
		if (!nsm)
		return;
		if (atomic_dec_and_test(&nsm->sm_count)) {
		mutex_lock(&nsm_mutex);
		if (atomic_read(&nsm->sm_count) == 0) {
		if (atomic_dec_and_test(&nsm->sm_count)) {
		list_del(&nsm->sm_link);
		kfree(nsm);
		}
		mutex_unlock(&nsm_mutex);
		}
		}