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Date: Tue, 23 Jul 2019 15:15:27 -0700
From: Kees Cook <keescook@...omium.org>
To: Ondrej Mosnacek <omosnace@...hat.com>
Cc: selinux@...r.kernel.org, Paul Moore <paul@...l-moore.com>,
	NitinGote <nitin.r.gote@...el.com>,
	kernel-hardening@...ts.openwall.com,
	William Roberts <bill.c.roberts@...il.com>
Subject: Re: [PATCH v2] selinux: check sidtab limit before adding a new entry

On Tue, Jul 23, 2019 at 08:50:59AM +0200, Ondrej Mosnacek wrote:
> We need to error out when trying to add an entry above SIDTAB_MAX in
> sidtab_reverse_lookup() to avoid overflow on the odd chance that this
> happens.
> 
> Fixes: ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve performance")
> Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  security/selinux/ss/sidtab.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
> index e63a90ff2728..1f0a6eaa2d6a 100644
> --- a/security/selinux/ss/sidtab.c
> +++ b/security/selinux/ss/sidtab.c
> @@ -286,6 +286,11 @@ static int sidtab_reverse_lookup(struct sidtab *s, struct context *context,
>  		++count;
>  	}
>  
> +	/* bail out if we already reached max entries */
> +	rc = -EOVERFLOW;
> +	if (count >= SIDTAB_MAX)
> +		goto out_unlock;
> +
>  	/* insert context into new entry */
>  	rc = -ENOMEM;
>  	dst = sidtab_do_lookup(s, count, 1);
> -- 
> 2.21.0
> 

-- 
Kees Cook

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