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x-sender="postmaster@mail.citrix.com"; x-conformance=sidf_compatible IronPort-SDR: Gli+TqwGxC/GYrRPCgNGxhfqKTVCvoT7k0/Pen5Lh1UUFrS/risYlnTDJoPX7tmq4BFJt6QAUq hr8IeK+EwJ5qCMZGkhzuvogSdKxNltfBgFQJbRQVQkCA766CjHBWRZCmdJRiuZBSe6AfOtTlwS 9LCuGogQ6Z4iEuV3MrV7hNBz3Ztq0UqvIBJaWhn3/O5UREMFPdLpidSh8Q3JUzbtdpPPHZSW3L ObnBhwNAeg4yVcwGOra0eedqQhDS8yTGB0dkK/VHSc0mu5I5mYmcVE/RLoCdPJ8rssr+7USspn Wvg= X-SBRS: 2.7 X-MesageID: 6317000 X-Ironport-Server: esa3.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.64,571,1559534400"; d="scan'208";a="6317000" From: Andrew Cooper To: Xen-devel Date: Tue, 1 Oct 2019 15:32:06 +0100 Message-ID: <20191001143207.15844-2-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20191001143207.15844-1-andrew.cooper3@citrix.com> References: <20191001143207.15844-1-andrew.cooper3@citrix.com> MIME-Version: 1.0 Subject: [Xen-devel] [PATCH v2 1/2] xen/nospec: Introduce CONFIG_SPECULATIVE_HARDEN_ARRAY X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Andrew Cooper , Wei Liu , Jan Beulich , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) There are legitimate circumstance where array hardening is not wanted or needed. Allow it to be turned off. Signed-off-by: Andrew Cooper Release-acked-by: Juergen Gross Reviewed-by: Jan Beulich --- CC: Jan Beulich CC: Wei Liu CC: Roger Pau Monn=C3=A9 CC: Juergen Gross v2: * Rename to CONFIG_SPECULATIVE_HARDEN_ARRAY * Simplify the stub array_index_nospec() --- xen/common/Kconfig | 24 ++++++++++++++++++++++++ xen/include/xen/nospec.h | 5 +++++ 2 files changed, 29 insertions(+) diff --git a/xen/common/Kconfig b/xen/common/Kconfig index 16829f6274..911333357a 100644 --- a/xen/common/Kconfig +++ b/xen/common/Kconfig @@ -77,6 +77,30 @@ config HAS_CHECKPOLICY string option env=3D"XEN_HAS_CHECKPOLICY" =20 +menu "Speculative hardening" + +config SPECULATIVE_HARDEN_ARRAY + bool "Speculative Array Hardening" + default y + ---help--- + Contemporary processors may use speculative execution as a + performance optimisation, but this can potentially be abused by an + attacker to leak data via speculative sidechannels. + + One source of data leakage is via speculative out-of-bounds array + accesses. + + When enabled, specific array accesses which have been deemed liable + to be speculatively abused will be hardened to avoid out-of-bounds + accesses. + + This is a best-effort mitigation. There are no guarantees that all + areas of code open to abuse have been hardened. + + If unsure, say Y. + +endmenu + config KEXEC bool "kexec support" default y diff --git a/xen/include/xen/nospec.h b/xen/include/xen/nospec.h index 2ac8feccc2..76255bc46e 100644 --- a/xen/include/xen/nospec.h +++ b/xen/include/xen/nospec.h @@ -33,6 +33,7 @@ static inline unsigned long array_index_mask_nospec(unsig= ned long index, } #endif =20 +#ifdef CONFIG_SPECULATIVE_HARDEN_ARRAY /* * array_index_nospec - sanitize an array index after a bounds check * @@ -58,6 +59,10 @@ static inline unsigned long array_index_mask_nospec(unsi= gned long index, \ (typeof(_i)) (_i & _mask); \ }) +#else +/* No index hardening. */ +#define array_index_nospec(index, size) ((void)(size), (index)) +#endif /* CONFIG_SPECULATIVE_HARDEN_ARRAY */ =20 /* * array_access_nospec - allow nospec access for static size arrays --=20 2.11.0 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel