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mm/hmm: Poison hmm_range during unregister 

Trying to misuse a range outside its lifetime is a kernel bug. Use poison
bytes to help detect this condition. Double unregister will reliably crash.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Tested-by: Philip Yang <Philip.Yang@amd.com>
This commit is contained in:
Jason Gunthorpe 2019-05-23 11:40:24 -03:00
parent 187229c2dd
commit 2dcc3eb8ab
1 changed files with 8 additions and 6 deletions
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14
mm/hmm.c
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@ -925,19 +925,21 @@ void hmm_range_unregister(struct hmm_range *range)
{
struct hmm *hmm = range->hmm;
/* Sanity check this really should not happen. */
if (hmm == NULL || range->end <= range->start)
return;
mutex_lock(&hmm->lock);
list_del_init(&range->list);
mutex_unlock(&hmm->lock);
/* Drop reference taken by hmm_range_register() */
range->valid = false;
mmput(hmm->mm);
hmm_put(hmm);
range->hmm = NULL;
/*
* The range is now invalid and the ref on the hmm is dropped, so
* poison the pointer. Leave other fields in place, for the caller's
* use.
*/
range->valid = false;
memset(&range->hmm, POISON_INUSE, sizeof(range->hmm));
}
EXPORT_SYMBOL(hmm_range_unregister);