diff options
author | Mel Gorman <mel@csn.ul.ie> | 2010-04-23 13:17:56 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-04-24 14:31:25 -0400 |
commit | 23be7468e8802a2ac1de6ee3eecb3ec7f14dc703 (patch) | |
tree | 2c01e547594b8d7f32ddda47b6bea284d8f19761 /mm/hugetlb.c | |
parent | 9a6a1ecd9e9b5d046a236da2f7eb6b6812f04229 (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')
-rw-r--r-- | mm/hugetlb.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 6034dc9e979..ffbdfc86aed 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c | |||
@@ -546,6 +546,7 @@ static void free_huge_page(struct page *page) | |||
546 | 546 | ||
547 | mapping = (struct address_space *) page_private(page); | 547 | mapping = (struct address_space *) page_private(page); |
548 | set_page_private(page, 0); | 548 | set_page_private(page, 0); |
549 | page->mapping = NULL; | ||
549 | BUG_ON(page_count(page)); | 550 | BUG_ON(page_count(page)); |
550 | INIT_LIST_HEAD(&page->lru); | 551 | INIT_LIST_HEAD(&page->lru); |
551 | 552 | ||
@@ -2447,8 +2448,10 @@ retry: | |||
2447 | spin_lock(&inode->i_lock); | 2448 | spin_lock(&inode->i_lock); |
2448 | inode->i_blocks += blocks_per_huge_page(h); | 2449 | inode->i_blocks += blocks_per_huge_page(h); |
2449 | spin_unlock(&inode->i_lock); | 2450 | spin_unlock(&inode->i_lock); |
2450 | } else | 2451 | } else { |
2451 | lock_page(page); | 2452 | lock_page(page); |
2453 | page->mapping = HUGETLB_POISON; | ||
2454 | } | ||
2452 | } | 2455 | } |
2453 | 2456 | ||
2454 | /* | 2457 | /* |