The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9795e0e8ac0d6a3ee092f1b555b284b57feef99e Mon Sep 17 00:00:00 2001 From: Jan Kara <jack@xxxxxxx> Date: Tue, 13 Jun 2017 15:54:58 +0200 Subject: [PATCH] udf: Fix races with i_size changes during readpage __udf_adinicb_readpage() uses i_size several times. When truncate changes i_size while the function is running, it can observe several different values and thus e.g. expose uninitialized parts of page to userspace. Also use i_size_read() in the function since it does not hold inode_lock. Since i_size is guaranteed to be small, this cannot really cause any issues even on 32-bit archs but let's be careful. CC: stable@xxxxxxxxxxxxxxx Fixes: 9c2fc0de1a6e638fe58c354a463f544f42a90a09 Signed-off-by: Jan Kara <jack@xxxxxxx> diff --git a/fs/udf/file.c b/fs/udf/file.c index f5eb2d5b3bac..e06d2c15749a 100644 --- a/fs/udf/file.c +++ b/fs/udf/file.c @@ -43,10 +43,15 @@ static void __udf_adinicb_readpage(struct page *page) struct inode *inode = page->mapping->host; char *kaddr; struct udf_inode_info *iinfo = UDF_I(inode); + loff_t isize = i_size_read(inode); + /* + * We have to be careful here as truncate can change i_size under us. + * So just sample it once and use the same value everywhere. + */ kaddr = kmap_atomic(page); - memcpy(kaddr, iinfo->i_ext.i_data + iinfo->i_lenEAttr, inode->i_size); - memset(kaddr + inode->i_size, 0, PAGE_SIZE - inode->i_size); + memcpy(kaddr, iinfo->i_ext.i_data + iinfo->i_lenEAttr, isize); + memset(kaddr + isize, 0, PAGE_SIZE - isize); flush_dcache_page(page); SetPageUptodate(page); kunmap_atomic(kaddr);