iomap: Fix possible overflow condition in iomap_write_delalloc_scan

riteshharjani · riteshharjani · commit eee2d2e6ea55 · 2023-07-25T10:55:55.000+05:30
folio_next_index() returns an unsigned long value which left shifted
by PAGE_SHIFT could possibly cause an overflow on 32-bit system. Instead
use folio_pos(folio) + folio_size(folio), which does this correctly.

Suggested-by: Matthew Wilcox &lt;willy@infradead.org&gt;
Signed-off-by: Ritesh Harjani (IBM) &lt;ritesh.list@gmail.com&gt;
Reviewed-by: Darrick J. Wong &lt;djwong@kernel.org&gt;
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
@@ -934,7 +934,7 @@ static int iomap_write_delalloc_scan(struct inode *inode,
 			 * the end of this data range, not the end of the folio.
 			 */
 			*punch_start_byte = min_t(loff_t, end_byte,
-					folio_next_index(folio) << PAGE_SHIFT);
+					folio_pos(folio) + folio_size(folio));
 		}
 
 		/* move offset to start of next folio in range */

Original file line number	Diff line number	Diff line change
`@@ -934,7 +934,7 @@ static int iomap_write_delalloc_scan(struct inode *inode,`
`934`	`934`	`* the end of this data range, not the end of the folio.`
`935`	`935`	`*/`
`936`	`936`	`*punch_start_byte = min_t(loff_t, end_byte,`
`937`		`- folio_next_index(folio) << PAGE_SHIFT);`
	`937`	`+ folio_pos(folio) + folio_size(folio));`
`938`	`938`	`}`
`939`	`939`
`940`	`940`	`/* move offset to start of next folio in range */`