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

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Message-ID: <ZdXfL8Kp4R/OT/VA@shell.armlinux.org.uk>
Date: Wed, 21 Feb 2024 11:31:59 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Kees Cook <keescook@...omium.org>
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,
	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 Wed, Feb 21, 2024 at 11:29:38AM +0000, Russell King (Oracle) wrote:
> On Tue, Feb 20, 2024 at 10:39:15PM -0800, Kees Cook wrote:
> > 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.
> 
> They can't show up in -next at the moment because the machine that hosts
> my git tree is being moved between data centres. This was originally
> flagged as a same-day (Tuesday) move, then next day, then it'll be back
> online on Saturday. That's the last update that we've had.
> 
> As I don't believe my GPG key has the necessary signatures on, I don't
> believe I can get a kernel.org account. I'm not even sure whether my
> gpg key is even correct for that - and at the moment I just glaze over
> reading the kernel.org gpg documentation.

I'll also point out that over the last two weeks, the first week I was
in Cambridge attending a conference at Arm Ltd, and then I went down
with full blown flu shortly there-after.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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