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From: Arend Van Spriel <>
To: Victor Bravo <>,
	Franky Lin <>,
	Hante Meuleman <>,
	Chi-Hsien Lin <>,
	Wright Feng <>,
	Kalle Valo <>,
	"David S. Miller" <>,,,,,
	Hans de Goede <>
Subject: Re: PROBLEM: brcmfmac's DMI-based fw file names break built-in fw loader
Date: Sat, 4 May 2019 21:11:09 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <20190504162633.ldrz2nqfocg55grb@localhost>

+ Hans, Luis

On 5/4/2019 6:26 PM, Victor Bravo wrote:
> The brcmfmac driver seems to have partially fixed problems which
> prevented it to be used in shared system/kernel images for multiple
> hardware by trying to load it's <config>.txt as
> <config>.<dmi_sys_vendor>.<dmi_product_name>.txt first and then
> falling back to <config>.txt. Real-life example:
> brcmfmac mmc1:0001:1: Direct firmware load for brcm/brcmfmac43340-sdio.ASUSTeK COMPUTER INC.-T100HAN.txt failed with
> error -2
> brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43340-sdio for chip
> BCM43340/2
> Unfortunately this doesn't really help on systems which use static
> kernel with firmware blobs (and also text configuration files in case of
> doesn't support spaces in file names - kernel build fails with
> CONFIG_EXTRA_FIRMWARE="brcm/brcmfmac43340-sdio.bin brcm/brcmfmac43340-sdio.ASUSTeK COMPUTER INC.-T100HAN.txt"
> for obvious reasons. So the only way here is to stay with good old
> brcmfmac43340-sdio.txt and support at most one brcmfmac-equipped machine
> per kernel image.
> Please consider filtering the DMI strings and replacing spaces and
> possibly other invalid characters with underscores, and/or adding module
> parameter to allow passing the string from command line (using
> brcmfmac.tag=t100 or brcmfmac.board=t100 to make the module load
> brcmfmac43340-sdio.t100.txt seems nicer to me, and isn't prone to
> breaking when DMI strings change on BIOS update).

The intent of the DMI approach was to avoid end-users from passing 
module parameters for this. As to fixing DMI string usage patches are 

> My brief grep-based research also suggest that strings retrieved
> by dmi_get_system_info() are passed to firmware loader without any
> checks for special character, /../ etc. I'm not sure whether this is
> considered to be proper & safe use, but if it's not, it may also have
> some security implications, as it allows attacker with access to DMI
> strings (using root rights/other OS/BIOS/physical access) to mess
> with kernel space or secure boot.

Hmm. Attackers with that kind of access can do bad is a gazillion ways.

> I would also really appreciate not allowing future brcm (and other)
> drivers to leave staging area before they fully support =y.

Define fully support. At the time we moved into the wireless tree 
(almost a decade ago) we did support =y. As such you could consider the 
DMI approach a regression, but I find that a bit harsh to say. Hans made 
a honest attempt and it is something that can be fixed. It can be you 
providing just that ;-)


  reply	other threads:[~2019-05-04 19:11 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-04 16:26 PROBLEM: brcmfmac's DMI-based fw file names break built-in fw loader Victor Bravo
2019-05-04 19:11 ` Arend Van Spriel [this message]
2019-05-04 19:44   ` Victor Bravo
2019-05-05  8:20     ` Arend Van Spriel
2019-05-05 14:36       ` Victor Bravo
2019-05-05 14:48       ` [PATCH RFC] brcmfmac: sanitize DMI strings Victor Bravo
2019-05-05 14:52         ` Victor Bravo
2019-05-05 15:03       ` [PATCH RFC] brcmfmac: sanitize DMI strings v2 Victor Bravo
2019-05-06  8:13         ` Hans de Goede
2019-05-06  8:42           ` Kalle Valo
2019-05-06  9:14             ` Victor Bravo
2019-05-06 12:29               ` Kalle Valo
2019-05-06 14:06                 ` Victor Bravo
2019-05-06  9:06           ` Victor Bravo
2019-05-06  9:33             ` Hans de Goede
2019-05-06 10:20               ` Victor Bravo
2019-05-06 10:34                 ` Hans de Goede
2019-05-06 12:26                   ` Kalle Valo
2019-05-06 15:24                     ` Victor Bravo
2019-05-06 16:05                       ` Hans de Goede
2019-05-06 19:30                         ` Arend Van Spriel
2019-05-07 15:38                           ` Hans de Goede
2019-05-13  9:21                             ` Arend Van Spriel
2019-05-06  8:44         ` Kalle Valo

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