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SUSE:SLE-12-SP1:GA
xen.8005
59087f4e-multicall-deal-with-early-exit-conditi...
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File 59087f4e-multicall-deal-with-early-exit-conditions.patch of Package xen.8005
References: bsc#1034843 XSA-213 # Commit 22c096c99d8c05833c3c19870e36efb2dd4e8013 # Date 2017-05-02 14:45:02 +0200 # Author Jan Beulich <jbeulich@suse.com> # Committer Jan Beulich <jbeulich@suse.com> multicall: deal with early exit conditions In particular changes to guest privilege level require the multicall sequence to be aborted, as hypercalls are permitted from kernel mode only. While likely not very useful in a multicall, also properly handle the return value in the HYPERVISOR_iret case (which should be the guest specified value). This is XSA-213. Reported-by: Jann Horn <jannh@google.com> Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> Acked-by: Julien Grall <julien.grall@arm.com> Index: xen-4.4.4-testing/xen/arch/arm/traps.c =================================================================== --- xen-4.4.4-testing.orig/xen/arch/arm/traps.c +++ xen-4.4.4-testing/xen/arch/arm/traps.c @@ -1236,30 +1236,33 @@ static bool_t check_multicall_32bit_clea return true; } -void do_multicall_call(struct multicall_entry *multi) +enum mc_disposition do_multicall_call(struct multicall_entry *multi) { arm_hypercall_fn_t call = NULL; if ( multi->op >= ARRAY_SIZE(arm_hypercall_table) ) { multi->result = -ENOSYS; - return; + return mc_continue; } call = arm_hypercall_table[multi->op].fn; if ( call == NULL ) { multi->result = -ENOSYS; - return; + return mc_continue; } if ( is_pv32_domain(current->domain) && !check_multicall_32bit_clean(multi) ) - return; + return mc_continue; multi->result = call(multi->args[0], multi->args[1], multi->args[2], multi->args[3], multi->args[4]); + + return likely(!psr_mode_is_user(guest_cpu_user_regs())) + ? mc_continue : mc_preempt; } /* Index: xen-4.4.4-testing/xen/common/multicall.c =================================================================== --- xen-4.4.4-testing.orig/xen/common/multicall.c +++ xen-4.4.4-testing/xen/common/multicall.c @@ -40,6 +40,7 @@ do_multicall( struct mc_state *mcs = ¤t->mc_state; uint32_t i; int rc = 0; + enum mc_disposition disp = mc_continue; if ( unlikely(__test_and_set_bit(_MCSF_in_multicall, &mcs->flags)) ) { @@ -50,7 +51,7 @@ do_multicall( if ( unlikely(!guest_handle_okay(call_list, nr_calls)) ) rc = -EFAULT; - for ( i = 0; !rc && i < nr_calls; i++ ) + for ( i = 0; !rc && disp == mc_continue && i < nr_calls; i++ ) { if ( i && hypercall_preempt_check() ) goto preempted; @@ -63,7 +64,7 @@ do_multicall( trace_multicall_call(&mcs->call); - do_multicall_call(&mcs->call); + disp = do_multicall_call(&mcs->call); #ifndef NDEBUG { @@ -77,7 +78,14 @@ do_multicall( } #endif - if ( unlikely(__copy_field_to_guest(call_list, &mcs->call, result)) ) + if ( unlikely(disp == mc_exit) ) + { + if ( __copy_field_to_guest(call_list, &mcs->call, result) ) + /* nothing, best effort only */; + rc = mcs->call.result; + } + else if ( unlikely(__copy_field_to_guest(call_list, &mcs->call, + result)) ) rc = -EFAULT; else if ( test_bit(_MCSF_call_preempted, &mcs->flags) ) { @@ -93,6 +101,9 @@ do_multicall( guest_handle_add_offset(call_list, 1); } + if ( unlikely(disp == mc_preempt) && i < nr_calls ) + goto preempted; + perfc_incr(calls_to_multicall); perfc_add(calls_from_multicall, i); mcs->flags = 0; Index: xen-4.4.4-testing/xen/include/asm-arm/multicall.h =================================================================== --- xen-4.4.4-testing.orig/xen/include/asm-arm/multicall.h +++ xen-4.4.4-testing/xen/include/asm-arm/multicall.h @@ -1,7 +1,11 @@ #ifndef __ASM_ARM_MULTICALL_H__ #define __ASM_ARM_MULTICALL_H__ -extern void do_multicall_call(struct multicall_entry *call); +extern enum mc_disposition { + mc_continue, + mc_exit, + mc_preempt, +} do_multicall_call(struct multicall_entry *call); #endif /* __ASM_ARM_MULTICALL_H__ */ /* Index: xen-4.4.4-testing/xen/include/asm-x86/multicall.h =================================================================== --- xen-4.4.4-testing.orig/xen/include/asm-x86/multicall.h +++ xen-4.4.4-testing/xen/include/asm-x86/multicall.h @@ -7,8 +7,21 @@ #include <xen/errno.h> +enum mc_disposition { + mc_continue, + mc_exit, + mc_preempt, +}; + +#define multicall_ret(call) \ + (unlikely((call)->op == __HYPERVISOR_iret) \ + ? mc_exit \ + : likely(guest_kernel_mode(current, \ + guest_cpu_user_regs())) \ + ? mc_continue : mc_preempt) + #define do_multicall_call(_call) \ - do { \ + ({ \ __asm__ __volatile__ ( \ " movq %c1(%0),%%rax; " \ " leaq hypercall_table(%%rip),%%rdi; " \ @@ -36,9 +49,11 @@ /* all the caller-saves registers */ \ : "rax", "rcx", "rdx", "rsi", "rdi", \ "r8", "r9", "r10", "r11" ); \ - } while ( 0 ) + multicall_ret(_call); \ + }) #define compat_multicall_call(_call) \ + ({ \ __asm__ __volatile__ ( \ " movl %c1(%0),%%eax; " \ " leaq compat_hypercall_table(%%rip),%%rdi; "\ @@ -65,6 +80,8 @@ "i" (offsetof(__typeof__(*_call), result)) \ /* all the caller-saves registers */ \ : "rax", "rcx", "rdx", "rsi", "rdi", \ - "r8", "r9", "r10", "r11" ) \ + "r8", "r9", "r10", "r11" ); \ + multicall_ret(_call); \ + }) #endif /* __ASM_X86_MULTICALL_H__ */
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