linux-kernel - Re: [PATCH] rtw89: Fix crash by loading compressed firmware file

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Date:   Fri, 05 Nov 2021 09:40:43 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Kalle Valo <kvalo@...eaurora.org>
Cc:     Takashi Iwai <tiwai@...e.de>, Ping-Ke Shih <pkshih@...ltek.com>,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        Larry Finger <Larry.Finger@...il.com>
Subject: Re: [PATCH] rtw89: Fix crash by loading compressed firmware file

On Fri, 05 Nov 2021 09:25:13 +0100,
Kalle Valo wrote:
> 
> Takashi Iwai <tiwai@...e.de> writes:
> 
> > On Fri, 05 Nov 2021 08:17:25 +0100,
> > Takashi Iwai wrote:
> >> 
> >> When a firmware is loaded in the compressed format or via user-mode
> >> helper, it's mapped in read-only, and the rtw89 driver crashes at
> >> rtw89_fw_download() when it tries to modify some data.
> >> 
> >> This patch is an attemp to avoid the crash by re-allocating the data
> >> via vmalloc() for the data modification.
> >
> > Alternatively, we may drop the code that modifies the loaded firmware
> > data?  At least SET_FW_HDR_PART_SIZE() in rtw89_fw_hdr_parser() looks
> > writing it, and I have no idea why this overwrite is needed.
> 
> Strange, isn't the firmware data marked as const just to avoid this kind
> of problem? Does rtw89 have wrong casts somewhere which removes the
> const?

Yes.  SET_FW_HDR_PART_SIZE() does the cast, dropping the const.


thanks,

Takashi