Commit cf47a83f authored by Jan Beulich's avatar Jan Beulich Committed by Konrad Rzeszutek Wilk
Browse files

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: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarJan 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: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 95a7d768

arch/x86/include/asm/xen/hypercall.h

+7 −14
Original line number Diff line number Diff line
@@ -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;

}

drivers/xen/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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)

drivers/xen/fallback.c

0 → 100644
+80 −0
Original line number Diff line number Diff line 
#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;

}

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