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Date: Mon, 22 Jul 2019 20:25:18 -0400
From: Paul Moore <>
To: Ondrej Mosnacek <>, NitinGote <>
Cc: Kees Cook <>,, 
	Stephen Smalley <>, Eric Paris <>, 
	SElinux list <>, 
	Linux kernel mailing list <>
Subject: Re: [PATCH] selinux: convert struct sidtab count to refcount_t

On Mon, Jul 22, 2019 at 9:18 AM Ondrej Mosnacek <> wrote:
> On Mon, Jul 22, 2019 at 1:35 PM NitinGote <> wrote:
> > refcount_t type and corresponding API should be
> > used instead of atomic_t when the variable is used as
> > a reference counter. This allows to avoid accidental
> > refcounter overflows that might lead to use-after-free
> > situations.
> >
> > Signed-off-by: NitinGote <>
> Nack.
> The 'count' variable is not used as a reference counter here. It
> tracks the number of entries in sidtab, which is a very specific
> lookup table that can only grow (the count never decreases). I only
> made it atomic because the variable is read outside of the sidtab's
> spin lock and thus the reads and writes to it need to be guaranteed to
> be atomic. The counter is only updated under the spin lock, so
> insertions do not race with each other.

Agreed, this should be changed to use refcount_t.

paul moore

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