[PATCH v2 hmm 09/11] mm/hmm: Poison hmm_range during unregister
Ira Weiny
ira.weiny at intel.com
Fri Jun 7 23:01:37 UTC 2019
On Thu, Jun 06, 2019 at 03:44:36PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg at mellanox.com>
>
> Trying to misuse a range outside its lifetime is a kernel bug. Use WARN_ON
> and poison bytes to detect this condition.
>
> Signed-off-by: Jason Gunthorpe <jgg at mellanox.com>
> Reviewed-by: Jérôme Glisse <jglisse at redhat.com>
> ---
> v2
> - Keep range start/end valid after unregistration (Jerome)
> ---
> mm/hmm.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 6802de7080d172..c2fecb3ecb11e1 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -937,7 +937,7 @@ 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)
> + if (WARN_ON(range->end <= range->start))
> return;
>
> mutex_lock(&hmm->lock);
> @@ -948,7 +948,10 @@ void hmm_range_unregister(struct hmm_range *range)
> range->valid = false;
> mmput(hmm->mm);
> hmm_put(hmm);
> - range->hmm = NULL;
> +
> + /* The range is now invalid, leave it poisoned. */
> + range->valid = false;
No need to set valid false again as you just did this 5 lines above.
Reviewed-by: Ira Weiny <ira.weiny at intel.com>
> + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm));
> }
> EXPORT_SYMBOL(hmm_range_unregister);
>
> --
> 2.21.0
>
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