nilfs2: initialize unused bytes in segment summary blocks

commit ef83274 upstream. Syzbot still reports uninit-value in nilfs_add_checksums_on_logs() for KMSAN enabled kernels after applying commit 7397031 ("nilfs2: initialize "struct nilfs_binfo_dat"->bi_pad field"). This is because the unused bytes at the end of each block in segment summaries are not initialized. So this fixes the issue by padding the unused bytes with null bytes. Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Ryusuke Konishi <[email protected]> Tested-by: Ryusuke Konishi <[email protected]> Reported-by: [email protected] Link: https://syzkaller.appspot.com/bug?extid=048585f3f4227bb2b49b Cc: Alexander Potapenko <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
ammarfaizi2 · Apr 25, 2023 · 9d3ba91 · 9d3ba91
1 parent 5b39e23
commit 9d3ba91
Showing 1 changed file with 20 additions and 0 deletions.
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
@@ -430,6 +430,23 @@ static int nilfs_segctor_reset_segment_buffer(struct nilfs_sc_info *sci)
 	return 0;
 }
 
+/**
+ * nilfs_segctor_zeropad_segsum - zero pad the rest of the segment summary area
+ * @sci: segment constructor object
+ *
+ * nilfs_segctor_zeropad_segsum() zero-fills unallocated space at the end of
+ * the current segment summary block.
+ */
+static void nilfs_segctor_zeropad_segsum(struct nilfs_sc_info *sci)
+{
+	struct nilfs_segsum_pointer *ssp;
+
+	ssp = sci->sc_blk_cnt > 0 ? &sci->sc_binfo_ptr : &sci->sc_finfo_ptr;
+	if (ssp->offset < ssp->bh->b_size)
+		memset(ssp->bh->b_data + ssp->offset, 0,
+		       ssp->bh->b_size - ssp->offset);
+}
+
 static int nilfs_segctor_feed_segment(struct nilfs_sc_info *sci)
 {
 	sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
@@ -438,6 +455,7 @@ static int nilfs_segctor_feed_segment(struct nilfs_sc_info *sci)
 				* The current segment is filled up
 				* (internal code)
 				*/
+	nilfs_segctor_zeropad_segsum(sci);
 	sci->sc_curseg = NILFS_NEXT_SEGBUF(sci->sc_curseg);
 	return nilfs_segctor_reset_segment_buffer(sci);
 }
@@ -542,6 +560,7 @@ static int nilfs_segctor_add_file_block(struct nilfs_sc_info *sci,
 		goto retry;
 	}
 	if (unlikely(required)) {
+		nilfs_segctor_zeropad_segsum(sci);
 		err = nilfs_segbuf_extend_segsum(segbuf);
 		if (unlikely(err))
 			goto failed;
@@ -1531,6 +1550,7 @@ static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
 		nadd = min_t(int, nadd << 1, SC_MAX_SEGDELTA);
 		sci->sc_stage = prev_stage;
 	}
+	nilfs_segctor_zeropad_segsum(sci);
 	nilfs_segctor_truncate_segments(sci, sci->sc_curseg, nilfs->ns_sufile);
 	return 0;