Commit 016eb4a0 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

[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 <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 3665d0e5
......@@ -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;
}
/**
......
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