| Message ID | 1481706707-6211-2-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | Accepted |
| Commit | f073bdc51771f5a5c7a8d1191bfc3ae371d44de7 |
| Headers | show |
On Wed, Dec 14, 2016 at 09:11:46AM +0000, Ard Biesheuvel wrote: > The VM_BUG_ON() check in move_freepages() checks whether the node > id of a page matches the node id of its zone. However, it does this > before having checked whether the struct page pointer refers to a > valid struct page to begin with. This is guaranteed in most cases, > but may not be the case if CONFIG_HOLES_IN_ZONE=y. > > So reorder the VM_BUG_ON() with the pfn_valid_within() check. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > mm/page_alloc.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index f64e7bcb43b7..4e298e31fa86 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1864,14 +1864,14 @@ int move_freepages(struct zone *zone, > #endif > > for (page = start_page; page <= end_page;) { > - /* Make sure we are not inadvertently changing nodes */ > - VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page); > - > if (!pfn_valid_within(page_to_pfn(page))) { > page++; > continue; > } > > + /* Make sure we are not inadvertently changing nodes */ > + VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page); > + > if (!PageBuddy(page)) { > page++; > continue; Acked-by: Will Deacon <will.deacon@arm.com> I'm guessing akpm can pick this up as a non-urgent fix. Will
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f64e7bcb43b7..4e298e31fa86 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1864,14 +1864,14 @@ int move_freepages(struct zone *zone, #endif for (page = start_page; page <= end_page;) { - /* Make sure we are not inadvertently changing nodes */ - VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page); - if (!pfn_valid_within(page_to_pfn(page))) { page++; continue; } + /* Make sure we are not inadvertently changing nodes */ + VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page); + if (!PageBuddy(page)) { page++; continue;
The VM_BUG_ON() check in move_freepages() checks whether the node id of a page matches the node id of its zone. However, it does this before having checked whether the struct page pointer refers to a valid struct page to begin with. This is guaranteed in most cases, but may not be the case if CONFIG_HOLES_IN_ZONE=y. So reorder the VM_BUG_ON() with the pfn_valid_within() check. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- mm/page_alloc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) -- 2.7.4