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openSUSE:12.2
xen
x86_64-allow-unsafe-adjust.patch
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File x86_64-allow-unsafe-adjust.patch of Package xen
References: CVE-2012-2934, bnc#764077 Product management demanded that customer systems must continue to boot irrespective of the presence of XSA-9. Rather than having our and perhaps other distros carry non-trivial patches, allow for more fine grained control (panic on boot, deny guest creation, or merely warn) by means of a single line change. --- a/xen/arch/x86/cpu/amd.c +++ b/xen/arch/x86/cpu/amd.c @@ -32,8 +32,11 @@ static char opt_famrev[14]; string_param("cpuid_mask_cpu", opt_famrev); -static int opt_allow_unsafe; +#ifdef __x86_64__ +/* 1 = allow, 0 = don't allow guest creation, -1 = don't allow boot */ +int __read_mostly opt_allow_unsafe; boolean_param("allow_unsafe", opt_allow_unsafe); +#endif static inline void wrmsr_amd(unsigned int index, unsigned int lo, unsigned int hi) @@ -623,10 +626,19 @@ static void __devinit init_amd(struct cp clear_bit(X86_FEATURE_MCE, c->x86_capability); #ifdef __x86_64__ - if (cpu_has_amd_erratum(c, AMD_ERRATUM_121) && !opt_allow_unsafe) + if (!cpu_has_amd_erratum(c, AMD_ERRATUM_121)) + opt_allow_unsafe = 1; + else if (opt_allow_unsafe < 0) panic("Xen will not boot on this CPU for security reasons.\n" "Pass \"allow_unsafe\" if you're trusting all your" " (PV) guest kernels.\n"); + else if (!opt_allow_unsafe && c == &boot_cpu_data) + printk(KERN_WARNING + "*** Xen will not allow creation of DomU-s on" + " this CPU for security reasons. ***\n" + KERN_WARNING + "*** Pass \"allow_unsafe\" if you're trusting" + " all your (PV) guest kernels. ***\n"); /* AMD CPUs do not support SYSENTER outside of legacy mode. */ clear_bit(X86_FEATURE_SEP, c->x86_capability); --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -52,6 +52,7 @@ #include <asm/traps.h> #include <asm/nmi.h> #include <asm/mce.h> +#include <asm/amd.h> #include <xen/numa.h> #include <xen/iommu.h> #ifdef CONFIG_COMPAT @@ -474,6 +475,20 @@ int arch_domain_create(struct domain *d, #else /* __x86_64__ */ + if ( d->domain_id && !is_idle_domain(d) && + cpu_has_amd_erratum(&boot_cpu_data, AMD_ERRATUM_121) ) + { + if ( !opt_allow_unsafe ) + { + printk(XENLOG_G_ERR "Xen does not allow DomU creation on this CPU" + " for security reasons.\n"); + return -EPERM; + } + printk(XENLOG_G_WARNING + "Dom%d may compromise security on this CPU.\n", + d->domain_id); + } + BUILD_BUG_ON(PDPT_L2_ENTRIES * sizeof(*d->arch.mm_perdomain_pt_pages) != PAGE_SIZE); pg = alloc_domheap_page(NULL, MEMF_node(domain_to_node(d))); --- a/xen/include/asm-x86/amd.h +++ b/xen/include/asm-x86/amd.h @@ -151,6 +151,8 @@ struct cpuinfo_x86; int cpu_has_amd_erratum(const struct cpuinfo_x86 *, int, ...); #ifdef __x86_64__ +extern int opt_allow_unsafe; + void fam10h_check_enable_mmcfg(void); void check_enable_amd_mmconf_dmi(void); #endif
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