linux-kernel - Re: [PATCH v2 2/2] misc: amd-sbi: Address copy_to/from

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Message-ID: <c5ea4e70-6a42-4d78-89b9-e8d65f214609@amd.com>
Date: Mon, 30 Jun 2025 17:02:22 +0530
From: "Gupta, Akshay" <Akshay.Gupta@....com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org, arnd@...db.de,
 shyam-sundar.s-k@....com, gautham.shenoy@....com, mario.limonciello@....com,
 naveenkrishna.chatradhi@....com, anand.umarji@....com
Subject: Re: [PATCH v2 2/2] misc: amd-sbi: Address copy_to/from_user() warning
 reported in smatch


On 6/25/2025 5:13 PM, Dan Carpenter wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
>
>
> On Wed, Jun 25, 2025 at 11:07:07AM +0000, Akshay Gupta wrote:
>> Smatch warnings are reported for below commit,
>>
>> Commit bb13a84ed6b7 ("misc: amd-sbi: Add support for CPUID protocol")
>> from Apr 28, 2025 (linux-next), leads to the following Smatch static
>> checker warning:
>>
>> drivers/misc/amd-sbi/rmi-core.c:376 apml_rmi_reg_xfer() warn: maybe return -EFAULT instead of the bytes remaining?
>> drivers/misc/amd-sbi/rmi-core.c:394 apml_mailbox_xfer() warn: maybe return -EFAULT instead of the bytes remaining?
>> drivers/misc/amd-sbi/rmi-core.c:411 apml_cpuid_xfer() warn: maybe return -EFAULT instead of the bytes remaining?
>> drivers/misc/amd-sbi/rmi-core.c:428 apml_mcamsr_xfer() warn: maybe return -EFAULT instead of the bytes remaining?
>>
>> copy_to/from_user() returns number of bytes, not copied.
>> In case data not copied, return "-EFAULT".
>>
>> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
>> Closes: https://lore.kernel.org/all/aDVyO8ByVsceybk9@stanley.mountain/
>> Reviewed-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@....com>
>> Signed-off-by: Akshay Gupta <akshay.gupta@....com>
>> ---
>> Changes from v1:
>>   - Split patch as per Greg's suggestion
>>   drivers/misc/amd-sbi/rmi-core.c | 15 +++++++++++----
>>   1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/misc/amd-sbi/rmi-core.c b/drivers/misc/amd-sbi/rmi-core.c
>> index 3570f3b269a9..9048517c088c 100644
>> --- a/drivers/misc/amd-sbi/rmi-core.c
>> +++ b/drivers/misc/amd-sbi/rmi-core.c
>> @@ -372,7 +372,8 @@ static int apml_rmi_reg_xfer(struct sbrmi_data *data,
>>        mutex_unlock(&data->lock);
>>
>>        if (msg.rflag && !ret)
> Unrelated to this patch, but it's always better to do if (ret) {.
> Do error handling not success handling etc.

Hi Dan,

Thank you for the suggestion, will take care of this.

>> -             return copy_to_user(arg, &msg, sizeof(struct apml_reg_xfer_msg));
>> +             if (copy_to_user(arg, &msg, sizeof(struct apml_reg_xfer_msg)))
>> +                     return -EFAULT;
>>        return ret;
>>   }
>>
>> @@ -390,7 +391,9 @@ static int apml_mailbox_xfer(struct sbrmi_data *data, struct apml_mbox_msg __use
>>        if (ret && ret != -EPROTOTYPE)
>>                return ret;
>>
>> -     return copy_to_user(arg, &msg, sizeof(struct apml_mbox_msg));
>> +     if (copy_to_user(arg, &msg, sizeof(struct apml_mbox_msg)))
>> +             return -EFAULT;
>> +     return ret;
> This fixes the -EPROTOTYPE as well.  In the original code, it would
> return success where -EPROTOTYPE was intended.  It's probably worth
> mentioning that in the commit message and maybe adding a test cases to
> your test platform.
I will update the commit message to address this.
> regards,
> dan carpenter
>