Re: [PATCH] ARM: fault: Implement copy_from_kernel_nofault_allowed()

Kees Cook
2024-02-21T06:39:17Z

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@kernel.org>
> Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]
> Suggested-by: "Russell King (Oracle)" <linux@armlinux.org.uk>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Wang Kefeng <wangkefeng.wang@huawei.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Ben Hutchings <ben@decadent.org.uk>
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Kees Cook <keescook@chromium.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