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Date: Mon, 22 Jul 2019 09:50:26 -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,
linux-security-module@...r.kernel.org
Subject: Re: [PATCH] selinux: check sidtab limit before adding a new entry
On Mon, Jul 22, 2019 at 03:21:11PM +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>
Is this reachable from unprivileged userspace?
> ---
> 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..54c1ba1e79ab 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 = -ENOMEM;
> + if (count == SIDTAB_MAX)
Do you want to use >= here instead?
-Kees
> + 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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