| Message ID | 20210312121653.348518-1-elver@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [mm] kfence: zero guard page after out-of-bounds access | expand |
On Fri, Mar 12, 2021 at 1:16 PM Marco Elver <elver@google.com> wrote: > > After an out-of-bounds accesses, zero the guard page before > re-protecting in kfence_guarded_free(). On one hand this helps make the > failure mode of subsequent out-of-bounds accesses more deterministic, > but could also prevent certain information leaks. > > Signed-off-by: Marco Elver <elver@google.com> Acked-by: Alexander Potapenko <glider@google.com> > --- > mm/kfence/core.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/kfence/core.c b/mm/kfence/core.c > index 3b8ec938470a..f7106f28443d 100644 > --- a/mm/kfence/core.c > +++ b/mm/kfence/core.c > @@ -371,6 +371,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z > > /* Restore page protection if there was an OOB access. */ > if (meta->unprotected_page) { > + memzero_explicit((void *)ALIGN_DOWN(meta->unprotected_page, PAGE_SIZE), PAGE_SIZE); > kfence_protect(meta->unprotected_page); > meta->unprotected_page = 0; > } > -- > 2.31.0.rc2.261.g7f71774620-goog >
diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 3b8ec938470a..f7106f28443d 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -371,6 +371,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z /* Restore page protection if there was an OOB access. */ if (meta->unprotected_page) { + memzero_explicit((void *)ALIGN_DOWN(meta->unprotected_page, PAGE_SIZE), PAGE_SIZE); kfence_protect(meta->unprotected_page); meta->unprotected_page = 0; }
After an out-of-bounds accesses, zero the guard page before re-protecting in kfence_guarded_free(). On one hand this helps make the failure mode of subsequent out-of-bounds accesses more deterministic, but could also prevent certain information leaks. Signed-off-by: Marco Elver <elver@google.com> --- mm/kfence/core.c | 1 + 1 file changed, 1 insertion(+)