linux-kernel - [PATCH v5 6/6] i3c: master: svc: fix possible assignment of the same address to two devices

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Message-Id: <20241001-svc-i3c-hj-v5-6-480ab8aed849@nxp.com>
Date: Tue, 01 Oct 2024 12:02:55 -0400
From: Frank Li <Frank.Li@....com>
To: Miquel Raynal <miquel.raynal@...tlin.com>, 
 Conor Culhane <conor.culhane@...vaco.com>, 
 Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 imx@...ts.linux.dev, Frank Li <Frank.Li@....com>, stable@...nel.org
Subject: [PATCH v5 6/6] i3c: master: svc: fix possible assignment of the
 same address to two devices

svc_i3c_master_do_daa() {
    ...
    for (i = 0; i < dev_nb; i++) {
        ret = i3c_master_add_i3c_dev_locked(m, addrs[i]);
        if (ret)
            goto rpm_out;
    }
}

If two devices (A and B) are detected in DAA and address 0xa is assigned to
device A and 0xb to device B, a failure in i3c_master_add_i3c_dev_locked()
for device A (addr: 0xa) could prevent device B (addr: 0xb) from being
registered on the bus. The I3C stack might still consider 0xb a free
address. If a subsequent Hotjoin occurs, 0xb might be assigned to Device A,
causing both devices A and B to use the same address 0xb, violating the I3C
specification.

The return value for i3c_master_add_i3c_dev_locked() should not be checked
because subsequent steps will scan the entire I3C bus, independent of
whether i3c_master_add_i3c_dev_locked() returns success.

If device A registration fails, there is still a chance to register device
B. i3c_master_add_i3c_dev_locked() can reset DAA if a failure occurs while
retrieving device information.

Cc: stable@...nel.org
Fixes: 317bacf960a4 ("i3c: master: add enable(disable) hot join in sys entry")
Reviewed-by: Miquel Raynal <miquel.raynal@...tlin.com>
Signed-off-by: Frank Li <Frank.Li@....com>
---
change from v3 to v4
- add comments about not check return value
- add miquel's review tag
---
 drivers/i3c/master/svc-i3c-master.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 3388c9af63fcc..7dc52111ee0f1 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -1103,12 +1103,27 @@ static int svc_i3c_master_do_daa(struct i3c_master_controller *m)
 	if (ret)
 		goto rpm_out;
 
-	/* Register all devices who participated to the core */
-	for (i = 0; i < dev_nb; i++) {
-		ret = i3c_master_add_i3c_dev_locked(m, addrs[i]);
-		if (ret)
-			goto rpm_out;
-	}
+	/*
+	 * Register all devices who participated to the core
+	 *
+	 * If two devices (A and B) are detected in DAA and address 0xa is assigned to
+	 * device A and 0xb to device B, a failure in i3c_master_add_i3c_dev_locked()
+	 * for device A (addr: 0xa) could prevent device B (addr: 0xb) from being
+	 * registered on the bus. The I3C stack might still consider 0xb a free
+	 * address. If a subsequent Hotjoin occurs, 0xb might be assigned to Device A,
+	 * causing both devices A and B to use the same address 0xb, violating the I3C
+	 * specification.
+	 *
+	 * The return value for i3c_master_add_i3c_dev_locked() should not be checked
+	 * because subsequent steps will scan the entire I3C bus, independent of
+	 * whether i3c_master_add_i3c_dev_locked() returns success.
+	 *
+	 * If device A registration fails, there is still a chance to register device
+	 * B. i3c_master_add_i3c_dev_locked() can reset DAA if a failure occurs while
+	 * retrieving device information.
+	 */
+	for (i = 0; i < dev_nb; i++)
+		i3c_master_add_i3c_dev_locked(m, addrs[i]);
 
 	/* Configure IBI auto-rules */
 	ret = svc_i3c_update_ibirules(master);

-- 
2.34.1