dm integrity: Use struct_group() to zero struct journal_sector

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark region of struct journal_sector that should be
initialized to zero.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index 7af242d..eb4b5e5 100644 (file)
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -121,8 +121,10 @@ struct journal_entry {
 #define JOURNAL_MAC_SIZE               (JOURNAL_MAC_PER_SECTOR * JOURNAL_BLOCK_SECTORS)
 
 struct journal_sector {
-       __u8 entries[JOURNAL_SECTOR_DATA - JOURNAL_MAC_PER_SECTOR];
-       __u8 mac[JOURNAL_MAC_PER_SECTOR];
+       struct_group(sectors,
+               __u8 entries[JOURNAL_SECTOR_DATA - JOURNAL_MAC_PER_SECTOR];
+               __u8 mac[JOURNAL_MAC_PER_SECTOR];
+       );
        commit_id_t commit_id;
 };
 
@@ -2870,7 +2872,8 @@ static void init_journal(struct dm_integrity_c *ic, unsigned start_section,
                wraparound_section(ic, &i);
                for (j = 0; j < ic->journal_section_sectors; j++) {
                        struct journal_sector *js = access_journal(ic, i, j);
-                       memset(&js->entries, 0, JOURNAL_SECTOR_DATA);
+                       BUILD_BUG_ON(sizeof(js->sectors) != JOURNAL_SECTOR_DATA);
+                       memset(&js->sectors, 0, sizeof(js->sectors));
                        js->commit_id = dm_integrity_commit_id(ic, i, j, commit_seq);
                }
                for (j = 0; j < ic->journal_section_entries; j++) {