From da574914df05176343a1f610c9edf30cd70dec0e Mon Sep 17 00:00:00 2001 From: Li Zhong Date: Wed, 6 Aug 2014 16:07:56 -0700 Subject: [PATCH] mm: fix potential infinite loop in dissolve_free_huge_pages() commit d0177639310d23c7739500df3c6ce6fdfe34acec upstream. It is possible for some platforms, such as powerpc to set HPAGE_SHIFT to 0 to indicate huge pages not supported. When this is the case, hugetlbfs could be disabled during boot time: hugetlbfs: disabling because there are no supported hugepage sizes Then in dissolve_free_huge_pages(), order is kept maximum (64 for 64bits), and the for loop below won't end: for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << order) As suggested by Naoya, below fix checks hugepages_supported() before calling dissolve_free_huge_pages(). [rientjes@google.com: no legitimate reason to call dissolve_free_huge_pages() when !hugepages_supported()] Signed-off-by: Li Zhong Acked-by: Naoya Horiguchi Acked-by: David Rientjes Signed-off-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 7a0a73d2fcff..7ae54449f252 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1089,6 +1089,9 @@ void dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn) unsigned long pfn; struct hstate *h; + if (!hugepages_supported()) + return; + /* Set scan step to minimum hugepage size */ for_each_hstate(h) if (order > huge_page_order(h))