From 955eff5acc8b8cd1c7d4eec0229c35eaabe013db Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Tue, 20 Feb 2007 13:58:08 -0800 Subject: [PATCH] fs: fix libfs data leak simple_prepare_write leaks uninitialised kernel data. This happens because the it leaves an uninitialised "hole" over the part of the page that the write is expected to go to. This is fine, but it then marks the page uptodate, which means a concurrent read can come in and copy the uninitialised memory into userspace before it written to. Fix it by simply marking it uptodate in simple_commit_write instead, after the hole has been filled in. This could theoretically break an fs that uses simple_prepare_write and not simple_commit_write, and that relies on the incorrect simple_prepare_write behaviour. Luckily, none of those exists in the tree. Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/libfs.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'fs') diff --git a/fs/libfs.c b/fs/libfs.c index 7d487047dbb8..cf79196535ec 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -335,17 +335,18 @@ int simple_prepare_write(struct file *file, struct page *page, flush_dcache_page(page); kunmap_atomic(kaddr, KM_USER0); } - SetPageUptodate(page); } return 0; } int simple_commit_write(struct file *file, struct page *page, - unsigned offset, unsigned to) + unsigned from, unsigned to) { struct inode *inode = page->mapping->host; loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; + if (!PageUptodate(page)) + SetPageUptodate(page); /* * No need to use i_size_read() here, the i_size * cannot change under us because we hold the i_mutex. -- cgit v1.2.3