* [PATCH] usb: typec: displayport: Fix potential deadlock
@ 2025-06-24 13:32 Andrei Kuchynski
2025-06-24 13:58 ` Heikki Krogerus
0 siblings, 1 reply; 2+ messages in thread
From: Andrei Kuchynski @ 2025-06-24 13:32 UTC (permalink / raw)
To: Heikki Krogerus, Jos Wang
Cc: Greg Kroah-Hartman, linux-usb, linux-kernel, Andrei Kuchynski,
stable
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@vger.kernel.org
Fixes: b4b38ffb38c9 ("usb: typec: displayport: Receive DP Status Update NAK request exit dp altmode")
Signed-off-by: Andrei Kuchynski <akuchynski@chromium.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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] usb: typec: displayport: Fix potential deadlock
2025-06-24 13:32 [PATCH] usb: typec: displayport: Fix potential deadlock Andrei Kuchynski
@ 2025-06-24 13:58 ` Heikki Krogerus
0 siblings, 0 replies; 2+ messages in thread
From: Heikki Krogerus @ 2025-06-24 13:58 UTC (permalink / raw)
To: Andrei Kuchynski
Cc: Jos Wang, Greg Kroah-Hartman, linux-usb, linux-kernel, stable
On Tue, Jun 24, 2025 at 01:32:46PM +0000, Andrei Kuchynski wrote:
> 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@vger.kernel.org
> Fixes: b4b38ffb38c9 ("usb: typec: displayport: Receive DP Status Update NAK request exit dp altmode")
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
> 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;
--
heikki
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