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xen/hypercall: fix hypercall fallback code for very old hypervisors 

While copying the argument structures in HYPERVISOR_event_channel_op()
and HYPERVISOR_physdev_op() into the local variable is sufficiently
safe even if the actual structure is smaller than the container one,
copying back eventual output values the same way isn't: This may
collide with on-stack variables (particularly "rc") which may change
between the first and second memcpy() (i.e. the second memcpy() could
discard that change).

Move the fallback code into out-of-line functions, and handle all of
the operations known by this old a hypervisor individually: Some don't
require copying back anything at all, and for the rest use the
individual argument structures' sizes rather than the container's.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
[v2: Reduce #define/#undef usage in HYPERVISOR_physdev_op_compat().]
[v3: Fix compile errors when modules use said hypercalls]
[v4: Add xen_ prefix to the HYPERCALL_..]
[v5: Alter the name and only EXPORT_SYMBOL_GPL one of them]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Jan Beulich 2012-10-19 15:25:37 -04:00 committed by Konrad Rzeszutek Wilk
parent 95a7d76897
commit cf47a83fb0
3 changed files with 88 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
arch/x86/include/asm/xen/hypercall.h
View File

@ -359,18 +359,14 @@ HYPERVISOR_update_va_mapping(unsigned long va, pte_t new_val,
return _hypercall4(int, update_va_mapping, va,
new_val.pte, new_val.pte >> 32, flags);
}
extern int __must_check xen_event_channel_op_compat(int, void *);
static inline int
HYPERVISOR_event_channel_op(int cmd, void *arg)
{
int rc = _hypercall2(int, event_channel_op, cmd, arg);
if (unlikely(rc == -ENOSYS)) {
struct evtchn_op op;
op.cmd = cmd;
memcpy(&op.u, arg, sizeof(op.u));
rc = _hypercall1(int, event_channel_op_compat, &op);
memcpy(arg, &op.u, sizeof(op.u));
}
if (unlikely(rc == -ENOSYS))
rc = xen_event_channel_op_compat(cmd, arg);
return rc;
}
@ -386,17 +382,14 @@ HYPERVISOR_console_io(int cmd, int count, char *str)
return _hypercall3(int, console_io, cmd, count, str);
}
extern int __must_check HYPERVISOR_physdev_op_compat(int, void *);
static inline int
HYPERVISOR_physdev_op(int cmd, void *arg)
{
int rc = _hypercall2(int, physdev_op, cmd, arg);
if (unlikely(rc == -ENOSYS)) {
struct physdev_op op;
op.cmd = cmd;
memcpy(&op.u, arg, sizeof(op.u));
rc = _hypercall1(int, physdev_op_compat, &op);
memcpy(arg, &op.u, sizeof(op.u));
}
if (unlikely(rc == -ENOSYS))
rc = HYPERVISOR_physdev_op_compat(cmd, arg);
return rc;
}

2
drivers/xen/Makefile
View File

@ -2,7 +2,7 @@ ifneq ($(CONFIG_ARM),y)
obj-y += manage.o balloon.o
obj-$(CONFIG_HOTPLUG_CPU) += cpu_hotplug.o
endif
obj-y += grant-table.o features.o events.o
obj-y += grant-table.o features.o events.o fallback.o
obj-y += xenbus/
nostackp := $(call cc-option, -fno-stack-protector)

80
drivers/xen/fallback.c Normal file
View File

@ -0,0 +1,80 @@
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/bug.h>
#include <linux/export.h>
#include <asm/hypervisor.h>
#include <asm/xen/hypercall.h>
int xen_event_channel_op_compat(int cmd, void *arg)
{
struct evtchn_op op;
int rc;
op.cmd = cmd;
memcpy(&op.u, arg, sizeof(op.u));
rc = _hypercall1(int, event_channel_op_compat, &op);
switch (cmd) {
case EVTCHNOP_close:
case EVTCHNOP_send:
case EVTCHNOP_bind_vcpu:
case EVTCHNOP_unmask:
/* no output */
break;
#define COPY_BACK(eop) \
case EVTCHNOP_##eop: \
memcpy(arg, &op.u.eop, sizeof(op.u.eop)); \
break
COPY_BACK(bind_interdomain);
COPY_BACK(bind_virq);
COPY_BACK(bind_pirq);
COPY_BACK(status);
COPY_BACK(alloc_unbound);
COPY_BACK(bind_ipi);
#undef COPY_BACK
default:
WARN_ON(rc != -ENOSYS);
break;
}
return rc;
}
EXPORT_SYMBOL_GPL(xen_event_channel_op_compat);
int HYPERVISOR_physdev_op_compat(int cmd, void *arg)
{
struct physdev_op op;
int rc;
op.cmd = cmd;
memcpy(&op.u, arg, sizeof(op.u));
rc = _hypercall1(int, physdev_op_compat, &op);
switch (cmd) {
case PHYSDEVOP_IRQ_UNMASK_NOTIFY:
case PHYSDEVOP_set_iopl:
case PHYSDEVOP_set_iobitmap:
case PHYSDEVOP_apic_write:
/* no output */
break;
#define COPY_BACK(pop, fld) \
case PHYSDEVOP_##pop: \
memcpy(arg, &op.u.fld, sizeof(op.u.fld)); \
break
COPY_BACK(irq_status_query, irq_status_query);
COPY_BACK(apic_read, apic_op);
COPY_BACK(ASSIGN_VECTOR, irq_op);
#undef COPY_BACK
default:
WARN_ON(rc != -ENOSYS);
break;
}
return rc;
}