From: Andrew Morton Date: Fri, 8 Sep 2006 16:48:38 +0000 (-0700) Subject: [PATCH] invalidate_complete_page() race fix X-Git-Tag: v2.6.18-rc7~19 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=016eb4a;p=linux-2.6 [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 --- diff --git a/mm/truncate.c b/mm/truncate.c index cf1b015df4..c6ab55ec68 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; } /**