[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.8] xen/arm: Turn on SILO mode by default on Arm
commit 7feb3ccccab3db1da12bb14be4eecbfe2bfffbb2 Author: Julien Grall <julien.grall@xxxxxxx> AuthorDate: Mon Apr 29 15:05:25 2019 +0100 Commit: Julien Grall <julien.grall@xxxxxxx> CommitDate: Fri Jun 14 15:46:00 2019 +0100 xen/arm: Turn on SILO mode by default on Arm On Arm, exclusive load-store atomics should only be used between trusted thread. As not all the guests are trusted, it may be possible to DoS Xen when updating shared memory with guest atomically. Recent patches introduced new helpers to update shared memory with guest atomically. Those helpers relies on a memory region to be be shared with Xen and a single guest. At the moment, nothing prevent a guest sharing a page with Xen and as well with another guest (e.g via grant table). For the scope of the XSA, the quickest way is to deny communications between unprivileged guest. So this patch is enabling and using SILO mode by default on Arm. Users wanted finer graine policy could wrote their own Flask policy. This is part of XSA-295. Signed-off-by: Julien Grall <julien.grall@xxxxxxx> Acked-by: Jan Beulich <jbeulich@xxxxxxxx> --- xen/arch/arm/setup.c | 8 ++++++-- xen/common/Kconfig | 3 ++- xen/include/xsm/xsm.h | 5 +++++ xen/xsm/xsm_core.c | 2 +- 4 files changed, 14 insertions(+), 4 deletions(-) diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c index 6116caa7ec..64143d34c5 100644 --- a/xen/arch/arm/setup.c +++ b/xen/arch/arm/setup.c @@ -38,6 +38,7 @@ #include <xen/vmap.h> #include <xen/libfdt/libfdt.h> #include <xen/acpi.h> +#include <xen/warning.h> #include <asm/alternative.h> #include <asm/page.h> #include <asm/current.h> @@ -801,8 +802,11 @@ void __init start_xen(unsigned long boot_phys_offset, tasklet_subsys_init(); - - xsm_dt_init(); + if ( xsm_dt_init() != 1 ) + warning_add("WARNING: SILO mode is not enabled.\n" + "It has implications on the security of the system,\n" + "unless the communications have been forbidden between\n" + "untrusted domains.\n"); init_maintenance_interrupt(); init_timer_interrupt(); diff --git a/xen/common/Kconfig b/xen/common/Kconfig index ac93928207..618e252351 100644 --- a/xen/common/Kconfig +++ b/xen/common/Kconfig @@ -87,7 +87,7 @@ config XENOPROF config XSM bool "Xen Security Modules support" - default n + default ARM ---help--- Enables the security framework known as Xen Security Modules which allows administrators fine-grained control over a Xen domain and @@ -152,6 +152,7 @@ config XSM_SILO choice prompt "Default XSM implementation" depends on XSM + default XSM_SILO_DEFAULT if XSM_SILO && ARM default XSM_FLASK_DEFAULT if XSM_FLASK default XSM_SILO_DEFAULT if XSM_SILO default XSM_DUMMY_DEFAULT diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h index 900d7d5f6e..06e7c22632 100644 --- a/xen/include/xsm/xsm.h +++ b/xen/include/xsm/xsm.h @@ -743,6 +743,11 @@ extern int xsm_multiboot_policy_init(unsigned long *module_map, #endif #ifdef CONFIG_HAS_DEVICE_TREE +/* + * Initialize XSM + * + * On success, return 1 if using SILO mode else 0. + */ extern int xsm_dt_init(void); extern int xsm_dt_policy_init(void **policy_buffer, size_t *policy_size); extern bool has_xsm_magic(paddr_t); diff --git a/xen/xsm/xsm_core.c b/xen/xsm/xsm_core.c index 91ef8a70b7..2a2100929d 100644 --- a/xen/xsm/xsm_core.c +++ b/xen/xsm/xsm_core.c @@ -164,7 +164,7 @@ int __init xsm_dt_init(void) xfree(policy_buffer); - return ret; + return ret ?: (xsm_bootparam == XSM_BOOTPARAM_SILO); } /** -- generated by git-patchbot for /home/xen/git/xen.git#stable-4.8 _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/xen-changelog
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