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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen master] multicall: deal with early exit conditions
commit 22c096c99d8c05833c3c19870e36efb2dd4e8013
Author: Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue May 2 14:45:02 2017 +0200
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue May 2 14:45:02 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>
---
xen/arch/arm/traps.c | 11 +++++++----
xen/arch/x86/pv/hypercall.c | 26 ++++++++++++++++++--------
xen/common/multicall.c | 17 ++++++++++++++---
xen/include/xen/multicall.h | 6 +++++-
4 files changed, 44 insertions(+), 16 deletions(-)
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 6bed039..6010c96 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1653,7 +1653,7 @@ static bool check_multicall_32bit_clean(struct
multicall_entry *multi)
return true;
}
-void arch_do_multicall_call(struct mc_state *state)
+enum mc_disposition arch_do_multicall_call(struct mc_state *state)
{
struct multicall_entry *multi = &state->call;
arm_hypercall_fn_t call = NULL;
@@ -1661,23 +1661,26 @@ void arch_do_multicall_call(struct mc_state *state)
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/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
index 9d29d2f..7c5e5a6 100644
--- a/xen/arch/x86/pv/hypercall.c
+++ b/xen/arch/x86/pv/hypercall.c
@@ -215,15 +215,19 @@ void pv_hypercall(struct cpu_user_regs *regs)
perfc_incr(hypercalls);
}
-void arch_do_multicall_call(struct mc_state *state)
+enum mc_disposition arch_do_multicall_call(struct mc_state *state)
{
- if ( !is_pv_32bit_vcpu(current) )
+ struct vcpu *curr = current;
+ unsigned long op;
+
+ if ( !is_pv_32bit_vcpu(curr) )
{
struct multicall_entry *call = &state->call;
- if ( (call->op < ARRAY_SIZE(pv_hypercall_table)) &&
- pv_hypercall_table[call->op].native )
- call->result = pv_hypercall_table[call->op].native(
+ op = call->op;
+ if ( (op < ARRAY_SIZE(pv_hypercall_table)) &&
+ pv_hypercall_table[op].native )
+ call->result = pv_hypercall_table[op].native(
call->args[0], call->args[1], call->args[2],
call->args[3], call->args[4], call->args[5]);
else
@@ -234,15 +238,21 @@ void arch_do_multicall_call(struct mc_state *state)
{
struct compat_multicall_entry *call = &state->compat_call;
- if ( (call->op < ARRAY_SIZE(pv_hypercall_table)) &&
- pv_hypercall_table[call->op].compat )
- call->result = pv_hypercall_table[call->op].compat(
+ op = call->op;
+ if ( (op < ARRAY_SIZE(pv_hypercall_table)) &&
+ pv_hypercall_table[op].compat )
+ call->result = pv_hypercall_table[op].compat(
call->args[0], call->args[1], call->args[2],
call->args[3], call->args[4], call->args[5]);
else
call->result = -ENOSYS;
}
#endif
+
+ return unlikely(op == __HYPERVISOR_iret)
+ ? mc_exit
+ : likely(guest_kernel_mode(curr, guest_cpu_user_regs()))
+ ? mc_continue : mc_preempt;
}
/*
diff --git a/xen/common/multicall.c b/xen/common/multicall.c
index cc8daf9..7cbf857 100644
--- a/xen/common/multicall.c
+++ b/xen/common/multicall.c
@@ -39,6 +39,7 @@ 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)) )
{
@@ -49,7 +50,7 @@ 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;
@@ -62,7 +63,7 @@ do_multicall(
trace_multicall_call(&mcs->call);
- arch_do_multicall_call(mcs);
+ disp = arch_do_multicall_call(mcs);
#ifndef NDEBUG
{
@@ -76,7 +77,14 @@ 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 ( current->hcall_preempted )
{
@@ -94,6 +102,9 @@ 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/xen/multicall.h b/xen/include/xen/multicall.h
index e8d7905..d0aa520 100644
--- a/xen/include/xen/multicall.h
+++ b/xen/include/xen/multicall.h
@@ -22,6 +22,10 @@ struct mc_state {
};
};
-void arch_do_multicall_call(struct mc_state *mc);
+enum mc_disposition {
+ mc_continue,
+ mc_exit,
+ mc_preempt,
+} arch_do_multicall_call(struct mc_state *mc);
#endif /* __XEN_MULTICALL_H__ */
--
generated by git-patchbot for /home/xen/git/xen.git#master
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