bcachefs: Fix invalid shift in member_to_text()

Reported-by: syzbot+064ce437a1ad63d3f6ef@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/sb-members.c

@@ -163,6 +163,11 @@ static int validate_member(struct printbuf *err,
 		return -BCH_ERR_invalid_sb_members;
 	}
 
+	if (m.btree_bitmap_shift >= 64) {
+		prt_printf(err, "device %u: invalid btree_bitmap_shift %u", i, m.btree_bitmap_shift);
+		return -BCH_ERR_invalid_sb_members;
+	}
+
 	return 0;
 }
 
@@ -247,7 +252,10 @@ static void member_to_text(struct printbuf *out,
 	prt_newline(out);
 
 	prt_printf(out, "Btree allocated bitmap blocksize:\t");
+	if (m.btree_bitmap_shift < 64)
 		prt_units_u64(out, 1ULL << m.btree_bitmap_shift);
+	else
+		prt_printf(out, "(invalid shift %u)", m.btree_bitmap_shift);
 	prt_newline(out);
 
 	prt_printf(out, "Btree allocated bitmap:\t");