On Wed, May 24, 2023 at 10:24 AM Lorenzo Stoakes <lstoakes@xxxxxxxxx> wrote: > > It turns out that alloc_pages_bulk_array() does not treat the page_array > parameter as an output parameter, but rather reads the array and skips any > entries that have already been allocated. > > This is somewhat unexpected and breaks this test, as we allocate the pages > array uninitialised on the assumption it will be overwritten. > > As a result, the test was referencing uninitialised data and causing the > PFN to not be valid and thus a WARN_ON() followed by a null pointer deref > and panic. > > In addition, this is an array of pointers not of struct page objects, so we > need only allocate an array with elements of pointer size. > > We solve both problems by simply using kcalloc() and referencing > sizeof(struct page *) rather than sizeof(struct page). > > Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx> > --- > lib/test_vmalloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c > index 9dd9745d365f..3718d9886407 100644 > --- a/lib/test_vmalloc.c > +++ b/lib/test_vmalloc.c > @@ -369,7 +369,7 @@ vm_map_ram_test(void) > int i; > > map_nr_pages = nr_pages > 0 ? nr_pages:1; > - pages = kmalloc(map_nr_pages * sizeof(struct page), GFP_KERNEL); > + pages = kcalloc(map_nr_pages, sizeof(struct page *), GFP_KERNEL); > if (!pages) > return -1; > > -- > 2.40.1 > Uh.. :) Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> -- Uladzislau Rezki
