linux-kernel - Re: [PATCH v2] char: tpm: tpm-buf: Add sanity check fallback in read helpers

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Message-ID: <66ecd791-959b-4eee-bf08-7331baca27d4@gmail.com>
Date: Thu, 10 Apr 2025 22:00:23 +0530
From: Purva Yeshi <purvayeshi550@...il.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: peterhuewe@....de, jgg@...pe.ca, linux-integrity@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] char: tpm: tpm-buf: Add sanity check fallback in read
 helpers

On 10/04/25 18:07, Jarkko Sakkinen wrote:
> On Thu, Apr 10, 2025 at 04:04:42PM +0530, Purva Yeshi wrote:
>> Fix Smatch-detected issue:
>>
>> drivers/char/tpm/tpm-buf.c:208 tpm_buf_read_u8() error:
>> uninitialized symbol 'value'.
>> drivers/char/tpm/tpm-buf.c:225 tpm_buf_read_u16() error:
>> uninitialized symbol 'value'.
>> drivers/char/tpm/tpm-buf.c:242 tpm_buf_read_u32() error:
>> uninitialized symbol 'value'.
>>
>> Zero-initialize the return values in tpm_buf_read_u8(),
>> tpm_buf_read_u16(), and tpm_buf_read_u32() to guard against
>> uninitialized data in case of a boundary overflow.
>>
>> Add defensive initialization ensures the return values are
>> always defined, preventing undefined behavior if the unexpected
>> happens.
>>
>> Signed-off-by: Purva Yeshi <purvayeshi550@...il.com>
>> ---
>> V1 - https://lore.kernel.org/all/20250409205536.210202-1-purvayeshi550@gmail.com/
>> V2 - Update commit message to clarify patch adds a sanity check
>>
>>   drivers/char/tpm/tpm-buf.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
>> index e49a19fea3bd..dc882fc9fa9e 100644
>> --- a/drivers/char/tpm/tpm-buf.c
>> +++ b/drivers/char/tpm/tpm-buf.c
>> @@ -201,7 +201,7 @@ static void tpm_buf_read(struct tpm_buf *buf, off_t *offset, size_t count, void
>>    */
>>   u8 tpm_buf_read_u8(struct tpm_buf *buf, off_t *offset)
>>   {
>> -	u8 value;
>> +	u8 value = 0;
>>   
>>   	tpm_buf_read(buf, offset, sizeof(value), &value);
>>   
>> @@ -218,7 +218,7 @@ EXPORT_SYMBOL_GPL(tpm_buf_read_u8);
>>    */
>>   u16 tpm_buf_read_u16(struct tpm_buf *buf, off_t *offset)
>>   {
>> -	u16 value;
>> +	u16 value = 0;
>>   
>>   	tpm_buf_read(buf, offset, sizeof(value), &value);
>>   
>> @@ -235,7 +235,7 @@ EXPORT_SYMBOL_GPL(tpm_buf_read_u16);
>>    */
>>   u32 tpm_buf_read_u32(struct tpm_buf *buf, off_t *offset)
>>   {
>> -	u32 value;
>> +	u32 value = 0;
>>   
>>   	tpm_buf_read(buf, offset, sizeof(value), &value);
>>   
>> -- 
>> 2.34.1
>>
>>
> 
> It's good and I think this change is appropriate overall!
> 
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
> 
> BR, Jarkko

Thank you for the review.

Best Regards,
Purva Yeshi