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 14:57:01 -0700 |
| commit | a988a1781479b17237042f9fa08bfe552fe592b0 (patch) | |
| tree | 3a6eaa133c6bc0d40766faec65ceb5821fa46d9c /mm/hugetlb.c | |
| parent | 5d5890b7cdde133721fc3050abd28085b8dbb2e3 (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/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 5d7601b0287..220c22acbe0 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -545,6 +545,7 @@ 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); @@ -2095,8 +2096,10 @@ 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; + } } /* |