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From: Paul Moore <>
To: Ondrej Mosnacek <>
Cc:, Jann Horn <>,
	NitinGote <>,
	Kees Cook <>
Subject: Re: [PATCH v2] selinux: avoid atomic_t usage in sidtab
Date: Tue, 27 Aug 2019 13:33:37 -0400
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, Aug 14, 2019 at 9:33 AM Ondrej Mosnacek <> wrote:
> As noted in Documentation/atomic_t.txt, if we don't need the RMW atomic
> operations, we should only use READ_ONCE()/WRITE_ONCE() +
> smp_rmb()/smp_wmb() where necessary (or the combined variants
> smp_load_acquire()/smp_store_release()).
> This patch converts the sidtab code to use regular u32 for the counter
> and reverse lookup cache and use the appropriate operations instead of
> atomic_get()/atomic_set(). Note that when reading/updating the reverse
> lookup cache we don't need memory barriers as it doesn't need to be
> consistent or accurate. We can now also replace some atomic ops with
> regular loads (when under spinlock) and stores (for conversion target
> fields that are always accessed under the master table's spinlock).
> We can now also bump SIDTAB_MAX to U32_MAX as we can use the full u32
> range again.
> Suggested-by: Jann Horn <>
> Signed-off-by: Ondrej Mosnacek <>
> Reviewed-by: Jann Horn <>
> ---
> v2: Added comments detailing access semantics of sidtab fields.
>  security/selinux/ss/sidtab.c | 48 ++++++++++++++++--------------------
>  security/selinux/ss/sidtab.h | 19 ++++++++++----
>  2 files changed, 35 insertions(+), 32 deletions(-)

Sorry for the delay on this, it was a casualty of LSS-NA.  Regardless,
this looks better, I just merged it into selinux/next - thanks!

paul moore

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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 13:33 Ondrej Mosnacek
2019-08-27 17:33 ` Paul Moore [this message]

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