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

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Message-ID: <CAEO-vhEwkQKnPprdw_r=mg6KRbadY6B4A3R_sOsyH0ds78wb2g@mail.gmail.com>
Date: Tue, 15 Oct 2024 16:48:18 -0600
From: "Everest K.C." <everestkc@...restkc.com.np>
To: Shuah Khan <skhan@...uxfoundation.org>
Cc: dpenkler@...il.com, gregkh@...uxfoundation.org, 
	linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: gpib: Move free after the variable use has been completed

On Tue, Oct 15, 2024 at 4:35 PM Shuah Khan <skhan@...uxfoundation.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@...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.
No, it was fixed in the linux-staging repo.
> Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>
>
> thanks,
> -- Shuah