| From | Ben Hutchings <> | Date | Mon, 09 Oct 2017 13:30:34 +0100 | Subject | [PATCH 3.2 11/74] udf: Fix races with i_size changes during readpage |
| |
3.2.94-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Jan Kara <jack@suse.cz>
commit 9795e0e8ac0d6a3ee092f1b555b284b57feef99e upstream.
__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.
Fixes: 9c2fc0de1a6e638fe58c354a463f544f42a90a09 Signed-off-by: Jan Kara <jack@suse.cz> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- fs/udf/file.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/fs/udf/file.c +++ b/fs/udf/file.c @@ -44,10 +44,15 @@ static void __udf_adinicb_readpage(struc 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(page); - memcpy(kaddr, iinfo->i_ext.i_data + iinfo->i_lenEAttr, inode->i_size); - memset(kaddr + inode->i_size, 0, PAGE_CACHE_SIZE - inode->i_size); + memcpy(kaddr, iinfo->i_ext.i_data + iinfo->i_lenEAttr, isize); + memset(kaddr + isize, 0, PAGE_CACHE_SIZE - isize); flush_dcache_page(page); SetPageUptodate(page); kunmap(page);
|