linux-kernel - [PATCH] usb: typec: displayport: Fix potential deadlock

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Message-ID: <20250624133246.3936737-1-akuchynski@chromium.org>
Date: Tue, 24 Jun 2025 13:32:46 +0000
From: Andrei Kuchynski <akuchynski@...omium.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Jos Wang <joswang@...ovo.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andrei Kuchynski <akuchynski@...omium.org>,
	stable@...r.kernel.org
Subject: [PATCH] usb: typec: displayport: Fix potential deadlock

The deadlock can occur due to a recursive lock acquisition of
`cros_typec_altmode_data::mutex`.
The call chain is as follows:
1. cros_typec_altmode_work() acquires the mutex
2. typec_altmode_vdm() -> dp_altmode_vdm() ->
3. typec_altmode_exit() -> cros_typec_altmode_exit()
4. cros_typec_altmode_exit() attempts to acquire the mutex again

To prevent this, defer the `typec_altmode_exit()` call by scheduling
it rather than calling it directly from within the mutex-protected
context.

Cc: stable@...r.kernel.org
Fixes: b4b38ffb38c9 ("usb: typec: displayport: Receive DP Status Update NAK request exit dp altmode")
Signed-off-by: Andrei Kuchynski <akuchynski@...omium.org>
---
 drivers/usb/typec/altmodes/displayport.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index b09b58d7311d..2abbe4de3216 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -394,8 +394,7 @@ static int dp_altmode_vdm(struct typec_altmode *alt,
 	case CMDT_RSP_NAK:
 		switch (cmd) {
 		case DP_CMD_STATUS_UPDATE:
-			if (typec_altmode_exit(alt))
-				dev_err(&dp->alt->dev, "Exit Mode Failed!\n");
+			dp->state = DP_STATE_EXIT;
 			break;
 		case DP_CMD_CONFIGURE:
 			dp->data.conf = 0;
-- 
2.50.0.rc2.761.g2dc52ea45b-goog