linux-kernel - Re: [PATCH 1/2] ARM: decompressor: support memory start validation for appended DTB

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACRpkdZhifRVB3vj1b1wZXcPwjnGFkLTnm1YOx34n36SYndCXg@mail.gmail.com>
Date: Sat, 20 Jan 2024 12:48:37 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Russell King <linux@...linux.org.uk>, Arnd Bergmann <arnd@...db.de>, 
	Andrew Morton <akpm@...ux-foundation.org>, Geert Uytterhoeven <geert+renesas@...der.be>, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Jonathan Corbet <corbet@....net>, 
	Thomas Gleixner <tglx@...utronix.de>, Randy Dunlap <rdunlap@...radead.org>, 
	"Mike Rapoport (IBM)" <rppt@...nel.org>, Eric DeVolder <eric.devolder@...cle.com>, 
	Nathan Chancellor <nathan@...nel.org>, "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>, 
	Kees Cook <keescook@...omium.org>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@...ainline.org>, John Crispin <john@...ozen.org>
Subject: Re: [PATCH 1/2] ARM: decompressor: support memory start validation
 for appended DTB

On Fri, Jan 19, 2024 at 9:14 PM Christian Marangi <ansuelsmth@...ilcom> wrote:

> There is currently a problem with a very specific sets of kernel config
> and AUTO_ZRELADDR.
>
> For the most common case AUTO_ZRELADDR check the PC register and
> calculate the start of the physical memory. Then fdt_check_mem_start is
> called to make sure the detected value makes sense by comparing it with
> what is present in DTB in the memory nodes and if additional fixup are
> required with the use of linux,usable-memory-range in the chosen node to
> hardcode usable memory range in case some reserved space needs to be
> addressed. With the help of this function the right address is
> calculated and the kernel correctly decompress and loads.
>
> Things starts to become problematic when in the mix,
> CONFIG_ARM_APPENDED_DTB is used. This is a particular kernel config is
> used when legacy systems doesn't support passing a DTB directly and a
> DTB is appended at the end of the image.
>
> In such case, fdt_check_mem_start is skipped in AUTO_ZRELADDR iteration
> as the appended DTB can be augumented later with ATAGS passed from the
> bootloader (if CONFIG_ARM_ATAG_DTB_COMPAT is enabled).
>
> The main problem and what this patch address is the fact that
> fdt_check_mem_start is never called later when the appended DTB is
> augumented, hence any fixup and validation is not done making AUTO_ZRELADDR
> detection inconsistent and most of the time wrong.
>
> Add support in head.S for this by checking if AUTO_ZRELADDR is enabled
> and calling fdt_check_mem_start with the appended DTB and the augumented
> values permitting legacy device to provide info in DTB instead of
> disabling AUTO_ZRELADDR and hardcoding the physical address offsets.
>
> Signed-off-by: Christian Marangi <ansuelsmth@...il.com>

Looks like the right solution to a very long-standing problem!
Thanks for your tireless hacking at this.
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij