Code: static int udf_symlink_filler(struct file *file, struct page *page)
{
 	struct inode *inode = page->mapping->host;
 	struct buffer_head *bh = NULL;
 	unsigned char *symlink;
	int err = -EIO;
 	unsigned char *p = kmap(page);
 	struct udf_inode_info *iinfo;
 	uint32_t pos;
 
 	iinfo = UDF_I(inode);
 	pos = udf_block_map(inode, 0);
 
	down_read(&iinfo->i_data_sem);
	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
		symlink = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
 	} else {
 		bh = sb_bread(inode->i_sb, pos);
 
		if (!bh)
			goto out;
 
 		symlink = bh->b_data;
 	}

	udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p);
	brelse(bh);

	up_read(&iinfo->i_data_sem);
	SetPageUptodate(page);
	kunmap(page);
 	unlock_page(page);
 	return 0;
 
out:
 	up_read(&iinfo->i_data_sem);
 	SetPageError(page);
 	kunmap(page);
 	unlock_page(page);
 	return err;
}

Commit Message: udf: Verify symlink size before loading it

UDF specification allows arbitrarily large symlinks. However we support
only symlinks at most one block large. Check the length of the symlink
so that we don't access memory beyond end of the symlink block.

CC: stable@vger.kernel.org
Reported-by: Carl Henrik Lunde <chlunde@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
CWE ID: CWE-119
static int udf_symlink_filler(struct file *file, struct page *page)
{
 	struct inode *inode = page->mapping->host;
 	struct buffer_head *bh = NULL;
 	unsigned char *symlink;
	int err;
 	unsigned char *p = kmap(page);
 	struct udf_inode_info *iinfo;
 	uint32_t pos;
 
	/* We don't support symlinks longer than one block */
	if (inode->i_size > inode->i_sb->s_blocksize) {
		err = -ENAMETOOLONG;
		goto out_unmap;
	}

 	iinfo = UDF_I(inode);
 	pos = udf_block_map(inode, 0);
 
	down_read(&iinfo->i_data_sem);
	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
		symlink = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
 	} else {
 		bh = sb_bread(inode->i_sb, pos);
 
		if (!bh) {
			err = -EIO;
			goto out_unlock_inode;
		}
 
 		symlink = bh->b_data;
 	}

	udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p);
	brelse(bh);

	up_read(&iinfo->i_data_sem);
	SetPageUptodate(page);
	kunmap(page);
 	unlock_page(page);
 	return 0;
 
out_unlock_inode:
 	up_read(&iinfo->i_data_sem);
 	SetPageError(page);
out_unmap:
 	kunmap(page);
 	unlock_page(page);
 	return err;
}
