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Commit 9795e0e8 authored by Jan Kara's avatar Jan Kara
Browse files

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@vger.kernel.org
Fixes: 9c2fc0de
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent a247f723

fs/udf/file.c

+7 −2
Original line number Diff line number Diff line
@@ -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);