linux-hardening - Re: [PATCH] ARM: fault: Implement copy_from_kernel_nofault

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Message-ID: <202402202235.A77C9AD@keescook>
Date: Tue, 20 Feb 2024 22:39:15 -0800
From: Kees Cook <keescook@...omium.org>
To: Russell King <linux@...linux.org.uk>
Cc: Mark Brown <broonie@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
	Wang Kefeng <wangkefeng.wang@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ben Hutchings <ben@...adent.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] ARM: fault: Implement copy_from_kernel_nofault_allowed()

On Mon, Jan 22, 2024 at 05:12:38PM -0800, Kees Cook wrote:
> Under PAN emulation when dumping backtraces from things like the
> LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
> would happen because of dump_instr() attempting to read a userspace
> address. Make sure copy_from_kernel_nofault() does not attempt this
> any more.
> 
> Reported-by: Mark Brown <broonie@...nel.org>
> Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]
> Suggested-by: "Russell King (Oracle)" <linux@...linux.org.uk>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: Wang Kefeng <wangkefeng.wang@...wei.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Ben Hutchings <ben@...adent.org.uk>
> Cc: linux-arm-kernel@...ts.infradead.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Russell, do you mind if I carry in my tree the 3 ARM patches I sent?
They're mostly pretty trivial, and they've been in "Incoming"[1] for 2
weeks but haven't shown up in -next yet. I'd really like them to get
some soak time, and for them to reach the v6.9 merge window in time.

Please let me know what you think. :) Thanks!

-Kees

[1] https://www.arm.linux.org.uk/developer/patches/section.php?section=0

-- 
Kees Cook