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From: Will Deacon <will@kernel.org>
To: George Spelvin <lkml@sdf.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2] arm64: ptr auth: Use get_random_u64 instead of _bytes
Date: Tue, 28 Apr 2020 13:58:12 +0100	[thread overview]
Message-ID: <20200428125812.GD6791@willie-the-truck> (raw)
In-Reply-To: <202003311544.02VFiClP011630@sdf.org>

Hi George,

On Tue, Mar 31, 2020 at 03:44:12PM +0000, George Spelvin wrote:
> get_random_bytes() is approximately 4x the cost of two
> get_random_u64() calls, because the former implements
> anti-backtracking.
> 
> Because these are authentication keys, useless to an attacker
> as soon as the kernel stops using them, there is no security
> benefit from anti-backtracking.
> 
> Signed-off-by: George Spelvin <lkml@sdf.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> ---
> v2: Took out all the clever bitmap-based stuff and made a simple
>     boring helper function to replace get_random_bytes(&key, 16).
> 
>  arch/arm64/include/asm/pointer_auth.h | 16 +++++++++++-----
>  arch/arm64/kernel/pointer_auth.c      | 10 +++++-----
>  2 files changed, 16 insertions(+), 10 deletions(-)

Please can you resend this against the arm64 for-next/ptr-auth branch [1]?
I can't apply it as-is.

Thanks,

Will

[1] https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/ptr-auth

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  parent reply	other threads:[~2020-04-28 12:58 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-31 15:44 [PATCH v2] arm64: ptr auth: Use get_random_u64 instead of _bytes George Spelvin
2020-03-31 16:22 ` Mark Rutland
2020-04-28 12:58 ` Will Deacon [this message]
2020-05-04 21:07   ` Will Deacon

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