IrqlExAllocatePool rule (wdm)

  • Article

The IrqlExAllocatePool rule specifies that the driver calls ExAllocatePoolWithTag and ExAllocatePoolWithTagPriority only when it is executing at IRQL<=DISPATCH_LEVEL.

A caller executing at DISPATCH_LEVEL must specify a NonPagedXxx value for PoolType. A caller executing at IRQL <= APC_LEVEL can specify any POOL_TYPE value.

Driver model: WDM

Bug check(s) found with this rule: Bug Check 0xC4: DRIVER_VERIFIER_DETECTED_VIOLATION (0x00020004), Bug Check 0xA: IRQL_NOT_LESS_OR_EQUAL

Example

In the following example, the ExAllocatePoolWithTag routine is called after the KeAcquireSpinLock routine, which sets IRQL to DISPATCH_LEVEL. The ExAllocatePoolWithTag routine is called with PagedPool, which violates the rule.

NTSTATUS
DispatchRequest (
    __in PDEVICE_REQUEST DeviceRequest
    )
{  
    KIRQL OldIrql;
    KSPIN_LOCK SpinLock;
    NTSTATUS Status;
    ...

    KeInitializeSpinLock(&SpinLock);

    //
    // KeAcquireSpinLock sets IRQL to DISPATCH_LEVEL and the previous IRQL is 
    // written to OldIrql after the lock is acquired.
    //

    KeAcquireSpinLock(&SpinLock, &OldIrql);
    ...

    Status = ProcessRequest(DeviceRequest);

    //
    // KeReleaseSpinLock sets IRQL to the OldIrql returned by KeAcquireSpinLock.
    //

    KeReleaseSpinLock(&SpinLock, &OldIrql);
    ...
}

NTSTATUS
ProcessRequest (
    __in PDEVICE_REQUEST DeviceRequest
    )
{
    NTSTATUS Status;
    ...

    //
    // RULE VIOLATION! - IrqlExAllocatePool executing at DISPATCH_LEVEL must specify 
    //                   a NonPagedXxx value for PoolType. 
    //

    DeviceRequest->Context = ExAllocatePool(PagedPool, sizeof(REQUEST_CONTEXT));
    if (DeviceRequest->Context == NULL) {
        Status = STATUS_INSUFFICIENT_RESOURCES;
    }
    ...

    return Status;
}

How to test

At compile time

Run Static Driver Verifier and specify the IrqlExAllocatePool rule.

Use the following steps to run an analysis of your code:
  1. Prepare your code (use role type declarations).
  2. Run Static Driver Verifier.
  3. View and analyze the results.

For more information, see Using Static Driver Verifier to Find Defects in Drivers.
At run time

Run Driver Verifier and select the DDI compliance checking option.

Applies to

ExAllocatePoolWithTag ExAllocatePoolWithTagPriority

See also

Managing Hardware Priorities Preventing Errors and Deadlocks While Using Spin Locks