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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Wed, 19 Jan 2022 23:45:55 +0200
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Subject: Re: [PATCH v3 3/9] brcmfmac: firmware: Do not crash on a NULL board_type
To:     Hector Martin <marcan@marcan.st>
Cc:     Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
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On Mon, Jan 17, 2022 at 4:30 PM Hector Martin <marcan@marcan.st> wrote:
>
> This unbreaks support for USB devices, which do not have a board_type
> to create an alt_path out of and thus were running into a NULL
> dereference.

In v5.16 we have two call sites:

1.
  if (cur->type == BRCMF_FW_TYPE_NVRAM && fwctx->req->board_type) {
    ...
    alt_path = brcm_alt_fw_path(cur->path, fwctx->req->board_type);

2.
  alt_path = brcm_alt_fw_path(first->path, fwctx->req->board_type);
  if (alt_path) {
    ...

Looking at them I would rather expect to see (as a quick fix, the
better solution is to unify those call sites by splitting out a common
helper):

  if (fwctx->req->board_type) {
    alt_path = brcm_alt_fw_path(first->path, fwctx->req->board_type);
  else
    alt_path = NULL;
   ...


> @@ -599,6 +599,9 @@ static char *brcm_alt_fw_path(const char *path, const char *board_type)
>         char alt_path[BRCMF_FW_NAME_LEN];
>         char suffix[5];
>
> +       if (!board_type)
> +               return NULL;


-- 
With Best Regards,
Andy Shevchenko