From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Kees Cook <keescook@chromium.org>,
kernel-hardening@lists.openwall.com,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org, Laura Abbott <labbott@redhat.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 0/2] arm64: optional paranoid __{get,put}_user checks
Date: Sat, 28 Oct 2017 09:47:30 +0100 [thread overview]
Message-ID: <20171028084729.GL20805@n2100.armlinux.org.uk> (raw)
In-Reply-To: <20171027154113.GA13737@arm.com>
On Fri, Oct 27, 2017 at 04:41:13PM +0100, Will Deacon wrote:
> Probably a stupid question, but why not just move the access_ok check
> into __{get,put}_user and remove it from {get,put}_user? We can also
> then move the uaccess_{enable,disable}_not_uao calls out from the __
> variants so that we can implement user_access_{begin,end}.
The intent of __{get,put}_user() is to have a fast accessor compared
to {get,put}_user() which does all the full checks.
However, with the uaccess stuff we have now by default, I don't think
it makes much sense - maybe we're better off using copy_{to,from}_user()
in those code paths and fixing up the struct in kernel space rather than
__{get,put}_user()?
I suspect that if we do have the full checks in __{get,put}_user() that
makes the case stronger for doing that - and maybe killing the __
accessors entirely.
Take a look at kernel/signal.c to see a typical usage of the __
accessors.
--
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next prev parent reply other threads:[~2017-10-28 8:47 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-26 9:09 [RFC PATCH 0/2] arm64: optional paranoid __{get,put}_user checks Mark Rutland
2017-10-26 9:09 ` [RFC PATCH 1/2] arm64: write __range_ok() in C Mark Rutland
2017-11-16 15:28 ` Will Deacon
2017-11-20 12:22 ` Mark Rutland
2017-10-26 9:09 ` [RFC PATCH 2/2] arm64: allow paranoid __{get,put}user Mark Rutland
2017-10-27 15:41 ` [RFC PATCH 0/2] arm64: optional paranoid __{get,put}_user checks Will Deacon
2017-10-27 20:44 ` Mark Rutland
2017-10-28 8:47 ` Russell King - ARM Linux [this message]
2017-10-31 23:56 ` Laura Abbott
2017-11-01 12:05 ` Mark Rutland
2017-11-01 21:13 ` Laura Abbott
2017-11-01 22:28 ` Kees Cook
2017-11-01 23:05 ` Laura Abbott
2017-11-01 23:29 ` Kees Cook
2017-11-02 1:25 ` Laura Abbott
2017-11-03 23:04 ` [RFC PATCH 1/2] x86: Avoid multiple evaluations in __{get,put}_user_size Laura Abbott
2017-11-03 23:04 ` [RFC PATCH 2/2] x86: Allow paranoid __{get,put}_user Laura Abbott
2017-11-04 0:14 ` Kees Cook
2017-11-04 0:24 ` Al Viro
2017-11-04 0:44 ` Al Viro
2017-11-04 1:39 ` Kees Cook
2017-11-04 1:41 ` Kees Cook
2017-11-04 1:58 ` Mark Rutland
2017-11-06 20:38 ` Laura Abbott
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