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

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Message-ID: <3a1c03c6-19da-4300-a56e-daf8264be064@gmail.com>
Date: Fri, 11 Apr 2025 14:31:30 +0530
From: Purva Yeshi <purvayeshi550@...il.com>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: peterhuewe@....de, jarkko@...nel.org, 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 11/04/25 12:50, Stefano Garzarella 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@...il.com/
>> V2 - Update commit message to clarify patch adds a sanity check
> 
> LGTM!
> 
> Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

Thank you for the review.

> 
>>
>> 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
>>
>>
> 

Best Regards,
Purva