Re: [PATCH] staging: gpib: Move free after the variable use has been completed

[Shuah Khan <skhan@linuxfoundation.org>]

On 10/15/24 16:48, Everest K.C. wrote:
> On Tue, Oct 15, 2024 at 4:35 PM Shuah Khan <skhan@linuxfoundation.org> wrote:
>>
>> On 10/15/24 15:51, Everest K.C. wrote:
>>> The variable `in_data` is freed, but used later in the code.
>>> Fix it by moving the freeing the memory after it use has been
>>> completed.
>>>
>>> This issue was reported by Coverity Scan.
>>> Report:
>>> CID 1600783: (#1 of 1): Use after free (USE_AFTER_FREE)
>>> 19. pass_freed_arg: Passing freed pointer in_data as an argument to
>>> ni_usb_dump_raw_block.
>>>
>>> Fixes: 4e127de14fa7 ("staging: gpib: Add National Instruments USB GPIB driver")
>>> Signed-off-by: Everest K.C. <everestkc@everestkc.com.np>
>>> ---
>>>    drivers/staging/gpib/ni_usb/ni_usb_gpib.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/staging/gpib/ni_usb/ni_usb_gpib.c b/drivers/staging/gpib/ni_usb/ni_usb_gpib.c
>>> index 1da263676f2a..75f39e1f3ed1 100644
>>> --- a/drivers/staging/gpib/ni_usb/ni_usb_gpib.c
>>> +++ b/drivers/staging/gpib/ni_usb/ni_usb_gpib.c
>>> @@ -690,12 +690,12 @@ static int ni_usb_read(gpib_board_t *board, uint8_t *buffer, size_t length,
>>>                kfree(in_data);
>>>                return parse_retval;
>>>        }
>>> -     kfree(in_data);
>>>        if (actual_length != length - status.count) {
>>>                pr_err("%s: actual_length=%i expected=%li\n",
>>>                       __func__, actual_length, (long)(length - status.count));
>>>                ni_usb_dump_raw_block(in_data, usb_bytes_read);
>>>        }
>>> +     kfree(in_data);
>>>        switch (status.error_code) {
>>>        case NIUSB_NO_ERROR:
>>>                retval = 0;
>>
>> Looks good to me. Isn't this on next though. Don't forget to
>> indicate it is against next.
> No, it was fixed in the linux-staging repo.
>> Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
>>

Okay - by the way the same problem is in ni_usb_write_registers().
Did coverity catch that one?

Both problems could be fix in one patch - I will leave it up to the
maintainers to make a call on two patches or a single patch.

thanks,
-- Shuah