[PATCH 4.4 56/58] mm: dont dereference struct page fields of invalid pages

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

--

From: Ard Biesheuvel 


[ Upstream commit f073bdc51771f5a5c7a8d1191bfc3ae371d44de7 ]

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.

Link: 
http://lkml.kernel.org/r/1481706707-6211-2-git-send-email-ard.biesheu...@linaro.org
Signed-off-by: Ard Biesheuvel 
Acked-by: Will Deacon 
Cc: Catalin Marinas 
Cc: Hanjun Guo 
Cc: Yisheng Xie 
Cc: Robert Richter 
Cc: James Morse 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman 
---
 mm/page_alloc.c |6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1527,14 +1527,14 @@ 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;

[PATCH 4.4 56/58] mm: dont dereference struct page fields of invalid pages

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

--

From: Ard Biesheuvel 


[ Upstream commit f073bdc51771f5a5c7a8d1191bfc3ae371d44de7 ]

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.

Link: 
http://lkml.kernel.org/r/1481706707-6211-2-git-send-email-ard.biesheu...@linaro.org
Signed-off-by: Ard Biesheuvel 
Acked-by: Will Deacon 
Cc: Catalin Marinas 
Cc: Hanjun Guo 
Cc: Yisheng Xie 
Cc: Robert Richter 
Cc: James Morse 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman 
---
 mm/page_alloc.c |6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1527,14 +1527,14 @@ 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;