ntfs3: Allocate iomap inline_data using alloc_page

This fixes a BUG reported in iomap_write_end_inline:
iomap_inline_data_valid checks that the inline_data fits within
a page. If the inline_data is allocated with kmemdup there's no
guarantee that it's page-aligned, so the check sometimes fails.
Allocate it with alloc_page to ensure it's page-aligned.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221446
Fixes: 099ef9a ("fs/ntfs3: implement iomap-based file operations")
Signed-off-by: Mihai Brodschi <m.brodschi@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

Author: m-brodschi

fs/ntfs3/attrib.c

@@ -1001,6 +1001,7 @@ int attr_data_get_block_locked(struct ntfs_inode *ni, CLST vcn, CLST clen,
 	struct ATTRIB *attr, *attr_b;
 	struct ATTR_LIST_ENTRY *le, *le_b;
 	struct mft_inode *mi, *mi_b;
+	struct page *page;
 	CLST hint, svcn, to_alloc, evcn1, next_svcn, asize, end, vcn0;
 	CLST alloc, evcn;
 	unsigned fr;
@@ -1036,10 +1037,13 @@ int attr_data_get_block_locked(struct ntfs_inode *ni, CLST vcn, CLST clen,
 		*lcn = RESIDENT_LCN;
 		*len = data_size;
 		if (res && data_size) {
-			*res = kmemdup(resident_data(attr_b), data_size,
-				       GFP_KERNEL);
-			if (!*res)
+			page = alloc_page(GFP_KERNEL);
+			if (!page) {
 				err = -ENOMEM;
+			} else {
+				*res = page_address(page);
+				memcpy(*res, resident_data(attr_b), data_size);
+			}
 		}
 		goto out;
 	}

fs/ntfs3/inode.c

@@ -796,7 +796,7 @@ static int ntfs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 
 	if (lcn == RESIDENT_LCN) {
 		if (offset >= clen) {
-			kfree(res);
+			__free_page(virt_to_page(res));
 			if (flags & IOMAP_REPORT) {
 				/* special code for report. */
 				return -ENOENT;
@@ -920,7 +920,7 @@ static int ntfs_iomap_end(struct inode *inode, loff_t pos, loff_t length,
 
 out:
 	if (iomap->type == IOMAP_INLINE) {
-		kfree(iomap->private);
+		__free_page(virt_to_page(iomap->private));
 		iomap->private = NULL;
 	}