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Date: Tue, 7 May 2024 14:02:35 -0700
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Subject: Re: [PATCH v1] usb: typec: tcpm: unregister existing source caps
 before re-registration
To: =?UTF-8?Q?Ond=C5=99ej_Jirman?= <megi@xff.cz>, linux@roeck-us.net,
 heikki.krogerus@linux.intel.com, gregkh@linuxfoundation.org,
 badhri@google.com, rdbabiera@google.com, linux-usb@vger.kernel.org,
 stable@vger.kernel.org, linux-kernel@vger.kernel.org,
 Mark Brown <broonie@kernel.org>
References: <20240424223227.1807844-1-amitsd@google.com>
 <y4lla7vqsrl75qhesmyexq7yvcu6hl6kryh3ctwq5ci3r4mlpw@rsnhfkmlmtt7>
Content-Language: en-US
From: Amit Sunil Dhamne <amitsd@google.com>
In-Reply-To: <y4lla7vqsrl75qhesmyexq7yvcu6hl6kryh3ctwq5ci3r4mlpw@rsnhfkmlmtt7>
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Hi Ondřej,

On 5/7/24 09:19, Ondřej Jirman wrote:
> On Wed, Apr 24, 2024 at 03:32:16PM GMT, Amit Sunil Dhamne wrote:
>> Check and unregister existing source caps in tcpm_register_source_caps
>> function before registering new ones. This change fixes following
>> warning when port partner resends source caps after negotiating PD contract
>> for the purpose of re-negotiation.
>>
>> [  343.135030][  T151] sysfs: cannot create duplicate filename '/devices/virtual/usb_power_delivery/pd1/source-capabilities'
>> [  343.135071][  T151] Call trace:
>> [  343.135076][  T151]  dump_backtrace+0xe8/0x108
>> [  343.135099][  T151]  show_stack+0x18/0x24
>> [  343.135106][  T151]  dump_stack_lvl+0x50/0x6c
>> [  343.135119][  T151]  dump_stack+0x18/0x24
>> [  343.135126][  T151]  sysfs_create_dir_ns+0xe0/0x140
>> [  343.135137][  T151]  kobject_add_internal+0x228/0x424
>> [  343.135146][  T151]  kobject_add+0x94/0x10c
>> [  343.135152][  T151]  device_add+0x1b0/0x4c0
>> [  343.135187][  T151]  device_register+0x20/0x34
>> [  343.135195][  T151]  usb_power_delivery_register_capabilities+0x90/0x20c
>> [  343.135209][  T151]  tcpm_pd_rx_handler+0x9f0/0x15b8
>> [  343.135216][  T151]  kthread_worker_fn+0x11c/0x260
>> [  343.135227][  T151]  kthread+0x114/0x1bc
>> [  343.135235][  T151]  ret_from_fork+0x10/0x20
>> [  343.135265][  T151] kobject: kobject_add_internal failed for source-capabilities with -EEXIST, don't try to register things with the same name in the same directory.
>>
>> Fixes: 8203d26905ee ("usb: typec: tcpm: Register USB Power Delivery Capabilities")
>> Cc: linux-usb@vger.kernel.org
>> Cc: stable@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Cc: Mark Brown <broonie@kernel.org>
>> Signed-off-by: Amit Sunil Dhamne <amitsd@google.com>
>> ---
>>   drivers/usb/typec/tcpm/tcpm.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
>> index ab6ed6111ed0..d8eb89f4f0c3 100644
>> --- a/drivers/usb/typec/tcpm/tcpm.c
>> +++ b/drivers/usb/typec/tcpm/tcpm.c
>> @@ -2996,7 +2996,7 @@ static int tcpm_register_source_caps(struct tcpm_port *port)
>>   {
>>   	struct usb_power_delivery_desc desc = { port->negotiated_rev };
>>   	struct usb_power_delivery_capabilities_desc caps = { };
>> -	struct usb_power_delivery_capabilities *cap;
>> +	struct usb_power_delivery_capabilities *cap = port->partner_source_caps;
>>   
>>   	if (!port->partner_pd)
>>   		port->partner_pd = usb_power_delivery_register(NULL, &desc);
>> @@ -3006,6 +3006,9 @@ static int tcpm_register_source_caps(struct tcpm_port *port)
>>   	memcpy(caps.pdo, port->source_caps, sizeof(u32) * port->nr_source_caps);
>>   	caps.role = TYPEC_SOURCE;
>>   
>> +	if (cap)
>> +		usb_power_delivery_unregister_capabilities(cap);
> This certainly looks like it's asking for use after free on port->partner_source_caps
> later on, since you're not clearing the pointer for the data that you just freed.
>
>> +
>>   	cap = usb_power_delivery_register_capabilities(port->partner_pd, &caps);
>>   	if (IS_ERR(cap))
>>   		return PTR_ERR(cap);
> This can easily fail if caps contain invalid PDOs, resulting in keeping pointer
> to freed memory in port->partner_source_caps.

Makes sense. I will send a fix for this. Thanks for the review.

Thanks,

Amit

>
> Kind regards,
> 	o.
>
>> base-commit: 0d31ea587709216d88183fe4ca0c8aba5e0205b8
>> -- 
>> 2.44.0.769.g3c40516874-goog
>>