diff options
| -rw-r--r-- | kernel/futex.c | 55 |
1 files changed, 45 insertions, 10 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 3019b92e691..52075633373 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -233,7 +233,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key) { unsigned long address = (unsigned long)uaddr; struct mm_struct *mm = current->mm; - struct page *page; + struct page *page, *page_head; int err; /* @@ -265,11 +265,46 @@ again: if (err < 0) return err; - page = compound_head(page); - lock_page(page); - if (!page->mapping) { - unlock_page(page); +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + page_head = page; + if (unlikely(PageTail(page))) { put_page(page); + /* serialize against __split_huge_page_splitting() */ + local_irq_disable(); + if (likely(__get_user_pages_fast(address, 1, 1, &page) == 1)) { + page_head = compound_head(page); + /* + * page_head is valid pointer but we must pin + * it before taking the PG_lock and/or + * PG_compound_lock. The moment we re-enable + * irqs __split_huge_page_splitting() can + * return and the head page can be freed from + * under us. We can't take the PG_lock and/or + * PG_compound_lock on a page that could be + * freed from under us. + */ + if (page != page_head) { + get_page(page_head); + put_page(page); + } + local_irq_enable(); + } else { + local_irq_enable(); + goto again; + } + } +#else + page_head = compound_head(page); + if (page != page_head) { + get_page(page_head); + put_page(page); + } +#endif + + lock_page(page_head); + if (!page_head->mapping) { + unlock_page(page_head); + put_page(page_head); goto again; } @@ -280,20 +315,20 @@ again: * it's a read-only handle, it's expected that futexes attach to * the object not the particular process. */ - if (PageAnon(page)) { + if (PageAnon(page_head)) { key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ key->private.mm = mm; key->private.address = address; } else { key->both.offset |= FUT_OFF_INODE; /* inode-based key */ - key->shared.inode = page->mapping->host; - key->shared.pgoff = page->index; + key->shared.inode = page_head->mapping->host; + key->shared.pgoff = page_head->index; } get_futex_key_refs(key); - unlock_page(page); - put_page(page); + unlock_page(page_head); + put_page(page_head); return 0; } |