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

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Message-ID: <99056bd3-748f-42e8-a25a-131f7b194f55@linuxfoundation.org>
Date: Tue, 15 Oct 2024 16:35:27 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: "Everest K.C." <everestkc@...restkc.com.np>, dpenkler@...il.com,
 gregkh@...uxfoundation.org
Cc: linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] staging: gpib: Move free after the variable use has been
 completed

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@...restkc.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.

Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah