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From:   Billy Tsai <billy_tsai@aspeedtech.com>
To:     <alexandre.belloni@bootlin.com>, <billy_tsai@aspeedtech.com>,
        <linux-i3c@lists.infradead.org>, <linux-kernel@vger.kernel.org>
CC:     <BMC-SW@aspeedtech.com>
Subject: [PATCH v1] i3c/master/mipi-i3c-hci: Fix a kernel panic for accessing DAT_data.
Date:   Mon, 23 Oct 2023 16:02:37 +0800
Message-ID: <20231023080237.560936-1-billy_tsai@aspeedtech.com>
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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>
---
 drivers/i3c/master/mipi-i3c-hci/dat_v1.c | 29 ++++++++++++++++--------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/drivers/i3c/master/mipi-i3c-hci/dat_v1.c b/drivers/i3c/master/mipi-i3c-hci/dat_v1.c
index 97bb49ff5b53..47b9b4d4ed3f 100644
--- a/drivers/i3c/master/mipi-i3c-hci/dat_v1.c
+++ b/drivers/i3c/master/mipi-i3c-hci/dat_v1.c
@@ -64,15 +64,17 @@ static int hci_dat_v1_init(struct i3c_hci *hci)
 		return -EOPNOTSUPP;
 	}
 
-	/* use a bitmap for faster free slot search */
-	hci->DAT_data = bitmap_zalloc(hci->DAT_entries, GFP_KERNEL);
-	if (!hci->DAT_data)
-		return -ENOMEM;
-
-	/* clear them */
-	for (dat_idx = 0; dat_idx < hci->DAT_entries; dat_idx++) {
-		dat_w0_write(dat_idx, 0);
-		dat_w1_write(dat_idx, 0);
+	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)
+			return -ENOMEM;
+
+		/* clear them */
+		for (dat_idx = 0; dat_idx < hci->DAT_entries; dat_idx++) {
+			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;
@@ -103,7 +111,8 @@ 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);
-	__clear_bit(dat_idx, hci->DAT_data);
+	if (hci->DAT_data)
+		__clear_bit(dat_idx, hci->DAT_data);
 }
 
 static void hci_dat_v1_set_dynamic_addr(struct i3c_hci *hci,
-- 
2.25.1