From: Jason Gunthorpe <[email protected]> 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 <[email protected]> Reviewed-by: Jérôme Glisse <[email protected]> Reviewed-by: John Hubbard <[email protected]> Acked-by: Souptick Joarder <[email protected]> Reviewed-by: Ralph Campbell <[email protected]> Reviewed-by: Ira Weiny <[email protected]> Tested-by: Philip Yang <[email protected]> --- v2 - Keep range start/end valid after unregistration (Jerome) v3 - Revise some comments (John) - Remove start/end WARN_ON (Souptick) v4 - Fix tabs vs spaces in comment (Christoph) --- mm/hmm.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index 2ef14b2b5505f6..c30aa9403dbe4d 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -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); -- 2.22.0 _______________________________________________ amd-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/amd-gfx
