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authorSudip Mukherjee <sudipm.mukherjee@gmail.com>2016-06-24 14:50:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-06-24 17:23:52 -0700
commit8285027fc479949a7a166bc1b26ce57e894878a7 (patch)
tree11874d42ed0637ce07ebc6f7739dfaa37bc12bd7
parent7c5b7239465932400ee0825bcc90624717c1af19 (diff)
downloadlinux-8285027fc479949a7a166bc1b26ce57e894878a7.tar.gz
mm/page_owner: avoid null pointer dereference
We have dereferenced page_ext before checking it. Lets check it first and then used it. Fixes: f86e4271978b ("mm: check the return value of lookup_page_ext for all call sites") Link: http://lkml.kernel.org/r/1465249059-7883-1-git-send-email-sudipm.mukherjee@gmail.com Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_owner.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/page_owner.c b/mm/page_owner.c
index c6cda3e36212..fedeba88c9cb 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -207,13 +207,15 @@ void __dump_page_owner(struct page *page)
.nr_entries = page_ext->nr_entries,
.entries = &page_ext->trace_entries[0],
};
- 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");