linux-kernel - Re: [PATCH] staging: rtl8723bs: fix memory leak error

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Date:   Thu, 2 Sep 2021 00:24:05 +0530
From:   "F.A. SULAIMAN" <asha.16@...ac.mrt.ac.lk>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8723bs: fix memory leak error

On Tue, Aug 31, 2021 at 2:18 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> On Tue, Aug 31, 2021 at 01:03:55AM +0530, F.A.Sulaiman wrote:
> > Smatch reported memory leak bug in rtl8723b_FirmwareDownload function.
> > The problem is pFirmware memory is not released in release_fw1.
> > Instead of redirecting to release_fw1 we can turn it into exit
> > and free the memory.
> >
> > Signed-off-by: F.A. SULAIMAN <asha.16@...ac.mrt.ac.lk>
> > ---
> >  drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c b/drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c
> > index de8caa6cd418..b59c2aa3a9d8 100644
> > --- a/drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c
> > +++ b/drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c
> > @@ -436,7 +436,7 @@ s32 rtl8723b_FirmwareDownload(struct adapter *padapter, bool  bUsedWoWLANFw)
> >       if (pFirmware->fw_length > FW_8723B_SIZE) {
> >               rtStatus = _FAIL;
> >               DBG_871X_LEVEL(_drv_emerg_, "Firmware size:%u exceed %u\n", pFirmware->fw_length, FW_8723B_SIZE);
> > -             goto release_fw1;
> > +             goto exit;
> >       }
>
> The current tree doesn't have DBG_871X_LEVEL() so you must be working
> against something old.  You need to work against linux-next or staging
> next.
>
> Your patch fixes a bug, but it would be better to just re-write the
> error handling for this function.  There is another bug that a bunch
> of error paths don't call release_firmware(fw).  Use the "Free the Last
> Thing" method.
>
>         pFirmware = kzalloc(sizeof(struct rt_firmware), GFP_KERNEL);
>         if (!pFirmware)
>                 return _FAIL;
>
> The last thing we allocated is "pFirmware" so free that if we have an
> error.
>
>         pBTFirmware = kzalloc(sizeof(struct rt_firmware), GFP_KERNEL);
>         if (!pBTFirmware) {
>                 rtStatus = _FAIL;
>                 goto free_firmware;
>         }
>
> Now the last thing is pBTFirmware.
>
>         rtStatus = request_firmware(&fw, fwfilepath, device);
>         if (rtStatus) {
>                 rtStatus = _FAIL;
>                 goto free_bt_firmware;
>         }
>
> Now the last thing is "fw".  But this is a bit tricky because we're
> going to release it as soon as possible and not wait until the end of
> the function.  There isn't a reason for this...  We can change that or
> keep it as-is.  If we keep it as is, then the we'll just call
> release_firmware(fw); before the goto free_bt_firmware;  The current
> code leaks fw on a bunch of error paths.
>
>         pFirmware->fw_buffer_sz = kmemdup(fw->data, fw->size, GFP_KERNEL);
>         if (!pFirmware->fw_buffer_sz) {
>                 rtStatus = _FAIL;
>                 release_firmware(fw);
>                 goto free_bt_firmware;
>         }
>
> Or:
>
>         pFirmware->fw_buffer_sz = kmemdup(fw->data, fw->size, GFP_KERNEL);
>         if (!pFirmware->fw_buffer_sz) {
>                 rtStatus = _FAIL;
>                 goto release_fw;
>         }
>
> Now the last thing is pFirmware->fw_buffer_sz.  Etc.
>
> Then at the end it's just:
>
> free_fw_buffer:
>         kfree(pFirmware->fw_buffer_sz);
> release_fw:
>         release_firmware(fw);
> free_bt_firmware:
>         kfree(pBTFirmware);
> free_firmware:
>         kfree(pFirmware);
>
>         return rtStatus;
> }
>

Thank you! I'll do the changes and send you a v2 patch.

Best Regards,
Asha Sulaiman.