From 016eb4a0ed06a3677d67a584da901f0e9a63c666 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Fri, 8 Sep 2006 09:48:38 -0700 Subject: [PATCH] [PATCH] invalidate_complete_page() race fix If a CPU faults this page into pagetables after invalidate_mapping_pages() checked page_mapped(), invalidate_complete_page() will still proceed to remove the page from pagecache. This leaves the page-faulting process with a detached page. If it was MAP_SHARED then file data loss will ensue. Fix that up by checking the page's refcount after taking tree_lock. Cc: Nick Piggin Cc: Hugh Dickins Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/truncate.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/mm/truncate.c b/mm/truncate.c index cf1b015df4a7..c6ab55ec6883 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -68,10 +68,10 @@ invalidate_complete_page(struct address_space *mapping, struct page *page) return 0; write_lock_irq(&mapping->tree_lock); - if (PageDirty(page)) { - write_unlock_irq(&mapping->tree_lock); - return 0; - } + if (PageDirty(page)) + goto failed; + if (page_count(page) != 2) /* caller's ref + pagecache ref */ + goto failed; BUG_ON(PagePrivate(page)); __remove_from_page_cache(page); @@ -79,6 +79,9 @@ invalidate_complete_page(struct address_space *mapping, struct page *page) ClearPageUptodate(page); page_cache_release(page); /* pagecache ref */ return 1; +failed: + write_unlock_irq(&mapping->tree_lock); + return 0; } /** -- 2.30.2