diff options
| author | Mel Gorman <mel@csn.ul.ie> | 2010-04-23 13:17:56 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-05-12 15:02:33 -0700 |
| commit | a340b55ae448daf36d110677c4cebd5897dbdf06 (patch) | |
| tree | 4ed17225bc05d13b09e1ccfecf432011f223e035 /mm | |
| parent | 8cae69607df46a03b65b533794f31a3259dced72 (diff) | |
hugetlb: fix infinite loop in get_futex_key() when backed by huge pages
commit 23be7468e8802a2ac1de6ee3eecb3ec7f14dc703 upstream.
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'mm')
| -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 2d16fa6b8c2..fd9ba95f06f 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; BUG_ON(page_count(page)); INIT_LIST_HEAD(&page->lru); @@ -2447,8 +2448,10 @@ retry: spin_lock(&inode->i_lock); inode->i_blocks += blocks_per_huge_page(h); spin_unlock(&inode->i_lock); - } else + } else { lock_page(page); + page->mapping = HUGETLB_POISON; + } } /* |