mm/hmm: fix use after free with struct hmm in the mmu notifiers
mmu_notifier_unregister_no_release() is not a fence and the mmu_notifier
system will continue to reference hmm->mn until the srcu grace period
expires.
Resulting in use after free races like this:
CPU0 CPU1
__mmu_notifier_invalidate_range_start()
srcu_read_lock
hlist_for_each ()
// mn == hmm->mn
hmm_mirror_unregister()
hmm_put()
hmm_free()
mmu_notifier_unregister_no_release()
hlist_del_init_rcu(hmm-mn->list)
mn->ops->invalidate_range_start(mn, range);
mm_get_hmm()
mm->hmm = NULL;
kfree(hmm)
mutex_lock(&hmm->lock);
Use SRCU to kfree the hmm memory so that the notifiers can rely on hmm
existing. Get the now-safe hmm struct through container_of and directly
check kref_get_unless_zero to lock it against free.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Philip Yang <Philip.Yang@amd.com>
2 files changed