On 06/17/2016 09:57 AM, js1304@xxxxxxxxx wrote:
From: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
We have dereferenced page_ext before checking it. Lets check it first
and then used it.
Link: http://lkml.kernel.org/r/1465249059-7883-1-git-send-email-sudipm.mukherjee@xxxxxxxxx
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@xxxxxxxxxxxxxxx>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Hmm, this is already in mmotm as
http://www.ozlabs.org/~akpm/mmotm/broken-out/mm-page_owner-use-stackdepot-to-store-stacktrace-fix.patch
But imho it's fixing a problem not related to your patch, but something that the
commit f86e4271978b missed. So it should separately go to 4.7 ASAP.
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Fixes: f86e4271978b ("mm: check the return value of lookup_page_ext for all call
sites")
---
mm/page_owner.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index dc92241..ec6dc18 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -295,13 +295,15 @@ void __dump_page_owner(struct page *page)
.skip = 0
};
depot_stack_handle_t handle;
- gfp_t gfp_mask = page_ext->gfp_mask;
- int mt = gfpflags_to_migratetype(gfp_mask);
+ gfp_t gfp_mask;
+ int mt;
if (unlikely(!page_ext)) {
pr_alert("There is not page extension available.\n");
return;
}
+ gfp_mask = page_ext->gfp_mask;
+ mt = gfpflags_to_migratetype(gfp_mask);
if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
pr_alert("page_owner info is not active (free page?)\n");
--
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