i3c: master: mipi-i3c-hci: Fix a kernel panic for accessing DAT_data.

The `i3c_master_bus_init` function may attach the I2C devices before the
I3C bus initialization. In this flow, the DAT `alloc_entry`` will be used
before the DAT `init`. Additionally, if the `i3c_master_bus_init` fails,
the DAT `cleanup` will execute before the device is detached, which will
execue DAT `free_entry` function. The above scenario can cause the driver
to use DAT_data when it is NULL.
Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Link: https://lore.kernel.org/r/20231023080237.560936-1-billy_tsai@aspeedtech.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/i3c/master/mipi-i3c-hci/dat_v1.c

@@ -64,6 +64,7 @@ static int hci_dat_v1_init(struct i3c_hci *hci)
 		return -EOPNOTSUPP;
 	}
 
+	if (!hci->DAT_data) {
 		/* use a bitmap for faster free slot search */
 		hci->DAT_data = bitmap_zalloc(hci->DAT_entries, GFP_KERNEL);
 		if (!hci->DAT_data)
@@ -74,6 +75,7 @@ static int hci_dat_v1_init(struct i3c_hci *hci)
 			dat_w0_write(dat_idx, 0);
 			dat_w1_write(dat_idx, 0);
 		}
+	}
 
 	return 0;
 }
@@ -87,7 +89,13 @@ static void hci_dat_v1_cleanup(struct i3c_hci *hci)
 static int hci_dat_v1_alloc_entry(struct i3c_hci *hci)
 {
 	unsigned int dat_idx;
+	int ret;
 
+	if (!hci->DAT_data) {
+		ret = hci_dat_v1_init(hci);
+		if (ret)
+			return ret;
+	}
 	dat_idx = find_first_zero_bit(hci->DAT_data, hci->DAT_entries);
 	if (dat_idx >= hci->DAT_entries)
 		return -ENOENT;
@@ -103,6 +111,7 @@ static void hci_dat_v1_free_entry(struct i3c_hci *hci, unsigned int dat_idx)
 {
 	dat_w0_write(dat_idx, 0);
 	dat_w1_write(dat_idx, 0);
+	if (hci->DAT_data)
 		__clear_bit(dat_idx, hci->DAT_data);
 }