[PATCH 3.16 21/47] VMCI: Fix integer overflow in VMCI handle arrays

Ben Hutchings
2019-10-25T18:10:54Z

From: Vishnu DASA <vdasa@vmware.com>

commit 1c2eb5b2853c9f513690ba6b71072d8eb65da16a upstream.

The VMCI handle array has an integer overflow in
vmci_handle_arr_append_entry when it tries to expand the array. This can be
triggered from a guest, since the doorbell link hypercall doesn't impose a
limit on the number of doorbell handles that a VM can create in the
hypervisor, and these handles are stored in a handle array.

In this change, we introduce a mandatory max capacity for handle
arrays/lists to avoid excessive memory usage.

Signed-off-by: Vishnu Dasa <vdasa@vmware.com>
Reviewed-by: Adit Ranadive <aditr@vmware.com>
Reviewed-by: Jorgen Hansen <jhansen@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/misc/vmw_vmci/vmci_context.c | 80 +++++++++++++----------
drivers/misc/vmw_vmci/vmci_handle_array.c | 38 +++++++----
drivers/misc/vmw_vmci/vmci_handle_array.h | 29 +++++---
include/linux/vmw_vmci_defs.h | 11 +++-
4 files changed, 99 insertions(+), 59 deletions(-)

--- a/drivers/misc/vmw_vmci/vmci_context.c
+++ b/drivers/misc/vmw_vmci/vmci_context.c
@@ -28,6 +28,9 @@
#include "vmci_driver.h"
#include "vmci_event.h"

+/* Use a wide upper bound for the maximum contexts. */
+#define VMCI_MAX_CONTEXTS 2000
+
/*
* List of current VMCI contexts. Contexts can be added by
* vmci_ctx_create() and removed via vmci_ctx_destroy().
@@ -124,19 +127,22 @@ struct vmci_ctx *vmci_ctx_create(u32 cid
/* Initialize host-specific VMCI context. */
init_waitqueue_head(&context->host_context.wait_queue);

- context->queue_pair_array = vmci_handle_arr_create(0);
+ context->queue_pair_array =
+ vmci_handle_arr_create(0, VMCI_MAX_GUEST_QP_COUNT);
if (!context->queue_pair_array) {
error = -ENOMEM;
goto err_free_ctx;
}

- context->doorbell_array = vmci_handle_arr_create(0);
+ context->doorbell_array =
+ vmci_handle_arr_create(0, VMCI_MAX_GUEST_DOORBELL_COUNT);
if (!context->doorbell_array) {
error = -ENOMEM;
goto err_free_qp_array;
}

- context->pending_doorbell_array = vmci_handle_arr_create(0);
+ context->pending_doorbell_array =
+ vmci_handle_arr_create(0, VMCI_MAX_GUEST_DOORBELL_COUNT);
if (!context->pending_doorbell_array) {
error = -ENOMEM;
goto err_free_db_array;
@@ -211,7 +217,7 @@ static int ctx_fire_notification(u32 con
* We create an array to hold the subscribers we find when
* scanning through all contexts.
*/
- subscriber_array = vmci_handle_arr_create(0);
+ subscriber_array = vmci_handle_arr_create(0, VMCI_MAX_CONTEXTS);
if (subscriber_array == NULL)
return VMCI_ERROR_NO_MEM;

@@ -630,20 +636,26 @@ int vmci_ctx_add_notification(u32 contex

spin_lock(&context->lock);

- list_for_each_entry(n, &context->notifier_list, node) {
- if (vmci_handle_is_equal(n->handle, notifier->handle)) {
- exists = true;
- break;
+ if (context->n_notifiers < VMCI_MAX_CONTEXTS) {
+ list_for_each_entry(n, &context->notifier_list, node) {
+ if (vmci_handle_is_equal(n->handle, notifier->handle)) {
+ exists = true;
+ break;
+ }
}
- }

- if (exists) {
- kfree(notifier);
- result = VMCI_ERROR_ALREADY_EXISTS;
+ if (exists) {
+ kfree(notifier);
+ result = VMCI_ERROR_ALREADY_EXISTS;
+ } else {
+ list_add_tail_rcu(&notifier->node,
+ &context->notifier_list);
+ context->n_notifiers++;
+ result = VMCI_SUCCESS;
+ }
} else {
- list_add_tail_rcu(&notifier->node, &context->notifier_list);
- context->n_notifiers++;
- result = VMCI_SUCCESS;
+ kfree(notifier);
+ result = VMCI_ERROR_NO_MEM;
}

spin_unlock(&context->lock);
@@ -728,8 +740,7 @@ static int vmci_ctx_get_chkpt_doorbells(
u32 *buf_size, void **pbuf)
{
struct dbell_cpt_state *dbells;
- size_t n_doorbells;
- int i;
+ u32 i, n_doorbells;

n_doorbells = vmci_handle_arr_get_size(context->doorbell_array);
if (n_doorbells > 0) {
@@ -867,7 +878,8 @@ int vmci_ctx_rcv_notifications_get(u32 c
spin_lock(&context->lock);

*db_handle_array = context->pending_doorbell_array;
- context->pending_doorbell_array = vmci_handle_arr_create(0);
+ context->pending_doorbell_array =
+ vmci_handle_arr_create(0, VMCI_MAX_GUEST_DOORBELL_COUNT);
if (!context->pending_doorbell_array) {
context->pending_doorbell_array = *db_handle_array;
*db_handle_array = NULL;
@@ -949,12 +961,11 @@ int vmci_ctx_dbell_create(u32 context_id
return VMCI_ERROR_NOT_FOUND;

spin_lock(&context->lock);
- if (!vmci_handle_arr_has_entry(context->doorbell_array, handle)) {
- vmci_handle_arr_append_entry(&context->doorbell_array, handle);
- result = VMCI_SUCCESS;
- } else {
+ if (!vmci_handle_arr_has_entry(context->doorbell_array, handle))
+ result = vmci_handle_arr_append_entry(&context->doorbell_array,
+ handle);
+ else
result = VMCI_ERROR_DUPLICATE_ENTRY;
- }

spin_unlock(&context->lock);
vmci_ctx_put(context);
@@ -1090,15 +1101,16 @@ int vmci_ctx_notify_dbell(u32 src_cid,
if (!vmci_handle_arr_has_entry(
dst_context->pending_doorbell_array,
handle)) {
- vmci_handle_arr_append_entry(
+ result = vmci_handle_arr_append_entry(
&dst_context->pending_doorbell_array,
handle);
-
- ctx_signal_notify(dst_context);
- wake_up(&dst_context->host_context.wait_queue);
-
+ if (result == VMCI_SUCCESS) {
+ ctx_signal_notify(dst_context);
+ wake_up(&dst_context->host_context.wait_queue);
+ }
+ } else {
+ result = VMCI_SUCCESS;
}
- result = VMCI_SUCCESS;
}
spin_unlock(&dst_context->lock);
}
@@ -1125,13 +1137,11 @@ int vmci_ctx_qp_create(struct vmci_ctx *
if (context == NULL || vmci_handle_is_invalid(handle))
return VMCI_ERROR_INVALID_ARGS;

- if (!vmci_handle_arr_has_entry(context->queue_pair_array, handle)) {
- vmci_handle_arr_append_entry(&context->queue_pair_array,
- handle);
- result = VMCI_SUCCESS;
- } else {
+ if (!vmci_handle_arr_has_entry(context->queue_pair_array, handle))
+ result = vmci_handle_arr_append_entry(
+ &context->queue_pair_array, handle);
+ else
result = VMCI_ERROR_DUPLICATE_ENTRY;
- }

return result;
}
--- a/drivers/misc/vmw_vmci/vmci_handle_array.c
+++ b/drivers/misc/vmw_vmci/vmci_handle_array.c
@@ -16,24 +16,29 @@
#include <linux/slab.h>
#include "vmci_handle_array.h"

-static size_t handle_arr_calc_size(size_t capacity)
+static size_t handle_arr_calc_size(u32 capacity)
{
- return sizeof(struct vmci_handle_arr) +
+ return VMCI_HANDLE_ARRAY_HEADER_SIZE +
capacity * sizeof(struct vmci_handle);
}

-struct vmci_handle_arr *vmci_handle_arr_create(size_t capacity)
+struct vmci_handle_arr *vmci_handle_arr_create(u32 capacity, u32 max_capacity)
{
struct vmci_handle_arr *array;

+ if (max_capacity == 0 || capacity > max_capacity)
+ return NULL;
+
if (capacity == 0)
- capacity = VMCI_HANDLE_ARRAY_DEFAULT_SIZE;
+ capacity = min((u32)VMCI_HANDLE_ARRAY_DEFAULT_CAPACITY,
+ max_capacity);

array = kmalloc(handle_arr_calc_size(capacity), GFP_ATOMIC);
if (!array)
return NULL;

array->capacity = capacity;
+ array->max_capacity = max_capacity;
array->size = 0;

return array;
@@ -44,27 +49,34 @@ void vmci_handle_arr_destroy(struct vmci
kfree(array);
}

-void vmci_handle_arr_append_entry(struct vmci_handle_arr **array_ptr,
- struct vmci_handle handle)
+int vmci_handle_arr_append_entry(struct vmci_handle_arr **array_ptr,
+ struct vmci_handle handle)
{
struct vmci_handle_arr *array = *array_ptr;

if (unlikely(array->size >= array->capacity)) {
/* reallocate. */
struct vmci_handle_arr *new_array;
- size_t new_capacity = array->capacity * VMCI_ARR_CAP_MULT;
- size_t new_size = handle_arr_calc_size(new_capacity);
+ u32 capacity_bump = min(array->max_capacity - array->capacity,
+ array->capacity);
+ size_t new_size = handle_arr_calc_size(array->capacity +
+ capacity_bump);
+
+ if (array->size >= array->max_capacity)
+ return VMCI_ERROR_NO_MEM;

new_array = krealloc(array, new_size, GFP_ATOMIC);
if (!new_array)
- return;
+ return VMCI_ERROR_NO_MEM;

- new_array->capacity = new_capacity;
+ new_array->capacity += capacity_bump;
*array_ptr = array = new_array;
}

array->entries[array->size] = handle;
array->size++;
+
+ return VMCI_SUCCESS;
}

/*
@@ -74,7 +86,7 @@ struct vmci_handle vmci_handle_arr_remov
struct vmci_handle entry_handle)
{
struct vmci_handle handle = VMCI_INVALID_HANDLE;
- size_t i;
+ u32 i;

for (i = 0; i < array->size; i++) {
if (vmci_handle_is_equal(array->entries[i], entry_handle)) {
@@ -109,7 +121,7 @@ struct vmci_handle vmci_handle_arr_remov
* Handle at given index, VMCI_INVALID_HANDLE if invalid index.
*/
struct vmci_handle
-vmci_handle_arr_get_entry(const struct vmci_handle_arr *array, size_t index)
+vmci_handle_arr_get_entry(const struct vmci_handle_arr *array, u32 index)
{
if (unlikely(index >= array->size))
return VMCI_INVALID_HANDLE;
@@ -120,7 +132,7 @@ vmci_handle_arr_get_entry(const struct v
bool vmci_handle_arr_has_entry(const struct vmci_handle_arr *array,
struct vmci_handle entry_handle)
{
- size_t i;
+ u32 i;

for (i = 0; i < array->size; i++)
if (vmci_handle_is_equal(array->entries[i], entry_handle))
--- a/drivers/misc/vmw_vmci/vmci_handle_array.h
+++ b/drivers/misc/vmw_vmci/vmci_handle_array.h
@@ -17,32 +17,41 @@
#define _VMCI_HANDLE_ARRAY_H_

#include <linux/vmw_vmci_defs.h>
+#include <linux/limits.h>
#include <linux/types.h>

-#define VMCI_HANDLE_ARRAY_DEFAULT_SIZE 4
-#define VMCI_ARR_CAP_MULT 2 /* Array capacity multiplier */
-
struct vmci_handle_arr {
- size_t capacity;
- size_t size;
+ u32 capacity;
+ u32 max_capacity;
+ u32 size;
+ u32 pad;
struct vmci_handle entries[];
};

-struct vmci_handle_arr *vmci_handle_arr_create(size_t capacity);
+#define VMCI_HANDLE_ARRAY_HEADER_SIZE \
+ offsetof(struct vmci_handle_arr, entries)
+/* Select a default capacity that results in a 64 byte sized array */
+#define VMCI_HANDLE_ARRAY_DEFAULT_CAPACITY 6
+/* Make sure that the max array size can be expressed by a u32 */
+#define VMCI_HANDLE_ARRAY_MAX_CAPACITY \
+ ((U32_MAX - VMCI_HANDLE_ARRAY_HEADER_SIZE - 1) / \
+ sizeof(struct vmci_handle))
+
+struct vmci_handle_arr *vmci_handle_arr_create(u32 capacity, u32 max_capacity);
void vmci_handle_arr_destroy(struct vmci_handle_arr *array);
-void vmci_handle_arr_append_entry(struct vmci_handle_arr **array_ptr,
- struct vmci_handle handle);
+int vmci_handle_arr_append_entry(struct vmci_handle_arr **array_ptr,
+ struct vmci_handle handle);
struct vmci_handle vmci_handle_arr_remove_entry(struct vmci_handle_arr *array,
struct vmci_handle
entry_handle);
struct vmci_handle vmci_handle_arr_remove_tail(struct vmci_handle_arr *array);
struct vmci_handle
-vmci_handle_arr_get_entry(const struct vmci_handle_arr *array, size_t index);
+vmci_handle_arr_get_entry(const struct vmci_handle_arr *array, u32 index);
bool vmci_handle_arr_has_entry(const struct vmci_handle_arr *array,
struct vmci_handle entry_handle);
struct vmci_handle *vmci_handle_arr_get_handles(struct vmci_handle_arr *array);

-static inline size_t vmci_handle_arr_get_size(
+static inline u32 vmci_handle_arr_get_size(
const struct vmci_handle_arr *array)
{
return array->size;
--- a/include/linux/vmw_vmci_defs.h
+++ b/include/linux/vmw_vmci_defs.h
@@ -75,9 +75,18 @@ enum {

/*
* A single VMCI device has an upper limit of 128MB on the amount of
- * memory that can be used for queue pairs.
+ * memory that can be used for queue pairs. Since each queue pair
+ * consists of at least two pages, the memory limit also dictates the
+ * number of queue pairs a guest can create.
*/
#define VMCI_MAX_GUEST_QP_MEMORY (128 * 1024 * 1024)
+#define VMCI_MAX_GUEST_QP_COUNT (VMCI_MAX_GUEST_QP_MEMORY / PAGE_SIZE / 2)
+
+/*
+ * There can be at most PAGE_SIZE doorbells since there is one doorbell
+ * per byte in the doorbell bitmap page.
+ */
+#define VMCI_MAX_GUEST_DOORBELL_COUNT PAGE_SIZE

/*
* Queues with pre-mapped data pages must be small, so that we don't pin