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udf: Fix races with i_size changes during readpage

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__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: 9c2fc0de1a
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jan Kara 2017-06-13 15:54:58 +02:00
parent a247f7236d
commit 9795e0e8ac
1 changed files with 7 additions and 2 deletions
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9
fs/udf/file.c
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@ -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);