bcachefs: Fix missing validation in bch2_sb_journal_v2_validate()

Reported-by: syzbot+47ecc948aadfb2ab3efc@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/journal_sb.c

@@ -104,6 +104,7 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
 	struct bch_sb_field_journal_v2 *journal = field_to_type(f, journal_v2);
 	struct bch_member m = bch2_sb_member_get(sb, sb->dev_idx);
 	int ret = -BCH_ERR_invalid_sb_journal;
+	u64 sum = 0;
 	unsigned nr;
 	unsigned i;
 	struct u64_range *b;
@@ -119,6 +120,15 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
 	for (i = 0; i < nr; i++) {
 		b[i].start = le64_to_cpu(journal->d[i].start);
 		b[i].end = b[i].start + le64_to_cpu(journal->d[i].nr);
+
+		if (b[i].end <= b[i].start) {
+			prt_printf(err, "journal buckets entry with bad nr: %llu+%llu",
+				   le64_to_cpu(journal->d[i].start),
+				   le64_to_cpu(journal->d[i].nr));
+			goto err;
+		}
+
+		sum += le64_to_cpu(journal->d[i].nr);
 	}
 
 	sort(b, nr, sizeof(*b), u64_range_cmp, NULL);
@@ -148,6 +158,11 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
 		}
 	}
 
+	if (sum > UINT_MAX) {
+		prt_printf(err, "too many journal buckets: %llu > %u", sum, UINT_MAX);
+		goto err;
+	}
+
 	ret = 0;
 err:
 	kfree(b);