path: root/mm/hugetlb.c
diff options
authorMel Gorman <mel@csn.ul.ie>2010-04-23 17:17:56 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2010-04-24 18:31:25 (GMT)
commit23be7468e8802a2ac1de6ee3eecb3ec7f14dc703 (patch)
tree2c01e547594b8d7f32ddda47b6bea284d8f19761 /mm/hugetlb.c
parent9a6a1ecd9e9b5d046a236da2f7eb6b6812f04229 (diff)
hugetlb: fix infinite loop in get_futex_key() when backed by huge pages
If a futex key happens to be located within a huge page mapped MAP_PRIVATE, get_futex_key() can go into an infinite loop waiting for a page->mapping that will never exist. See https://bugzilla.redhat.com/show_bug.cgi?id=552257 for more details about the problem. This patch makes page->mapping a poisoned value that includes PAGE_MAPPING_ANON mapped MAP_PRIVATE. This is enough for futex to continue but because of PAGE_MAPPING_ANON, the poisoned value is not dereferenced or used by futex. No other part of the VM should be dereferencing the page->mapping of a hugetlbfs page as its page cache is not on the LRU. This patch fixes the problem with the test case described in the bugzilla. [akpm@linux-foundation.org: mel cant spel] Signed-off-by: Mel Gorman <mel@csn.ul.ie> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Darren Hart <darren@dvhart.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6034dc9..ffbdfc8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -546,6 +546,7 @@ static void free_huge_page(struct page *page)
mapping = (struct address_space *) page_private(page);
set_page_private(page, 0);
+ page->mapping = NULL;
@@ -2447,8 +2448,10 @@ retry:
inode->i_blocks += blocks_per_huge_page(h);
- } else
+ } else {
+ page->mapping = HUGETLB_POISON;
+ }

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