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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.6] multicall: deal with early exit conditions
commit fc7839698c0a9375bbe7f493702322d1a1de4663
Author: Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue May 2 15:01:12 2017 +0200
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue May 2 15:01:12 2017 +0200
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@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>
master commit: 22c096c99d8c05833c3c19870e36efb2dd4e8013
master date: 2017-05-02 14:45:02 +0200
---
xen/arch/arm/traps.c | 11 +++++++----
xen/common/multicall.c | 17 ++++++++++++++---
xen/include/asm-arm/multicall.h | 6 +++++-
xen/include/asm-x86/multicall.h | 23 ++++++++++++++++++++---
4 files changed, 46 insertions(+), 11 deletions(-)
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 5499493..551409a 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1504,30 +1504,33 @@ static bool_t check_multicall_32bit_clean(struct
multicall_entry *multi)
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_32bit_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;
}
/*
diff --git a/xen/common/multicall.c b/xen/common/multicall.c
index fa9d910..da13573 100644
--- a/xen/common/multicall.c
+++ b/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;
diff --git a/xen/include/asm-arm/multicall.h b/xen/include/asm-arm/multicall.h
index b959262..ee3b345 100644
--- a/xen/include/asm-arm/multicall.h
+++ b/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__ */
/*
diff --git a/xen/include/asm-x86/multicall.h b/xen/include/asm-x86/multicall.h
index fcd0ea5..3cb0b6d 100644
--- a/xen/include/asm-x86/multicall.h
+++ b/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; " \
@@ -37,9 +50,11 @@
/* 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; "\
@@ -67,6 +82,8 @@
"i" (-ENOSYS) \
/* 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__ */
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6
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