Re: [ros-dev] [ros-diffs] [gedmurphy] 70408: [NTOSKRNL] - Raise the IRQL when enumerating device lists so it doesn't get edited mid-listing - Don't hardcode the pointer size when checking the buffer size

[Ged Murphy]

It depends on whether we want to emulate the 2k3 kernel or not.

I noticed in my 2k3 fltmgr testing that IoEnumerateDeviceObjectList runs at
DPC for the entirety of the function. This was changed in the NT6 kernel to
use a lock, which is indeed the LockQueueIoDatabaseLock Hermes mentioned.

I'm happy to use the spinlock (and would prefer to myself), but any move
towards NT6 normally results in an angry email, so I opted for the 2k3
approach  ;)

Ged.


-----Original Message-----
From: Ros-dev [mailto:[e-mail]] On Behalf Of Hermès
BÉLUSCA - MAÏTO
Sent: 29 December 2015 16:08
To: 'ReactOS Development List' <ros-dev(a)reactos.org>
Subject: Re: [ros-dev] [ros-diffs] [gedmurphy] 70408: [NTOSKRNL] - Raise the
IRQL when enumerating device lists so it doesn't get edited mid-listing -
Don't hardcode the pointer size when checking the buffer size

Yes this should be a spinlock involved instead, for example the
"LockQueueIoDatabaseLock" (queued) spinlock that we already use in other
places in the code.

-----Message d'origine-----
De : Ros-dev [mailto:[e-mail]] De la part de Thomas Faber
Envoyé : mardi 29 décembre 2015 13:20 À : ros-dev(a)reactos.org Objet : Re:
[ros-dev] [ros-diffs] [gedmurphy] 70408: [NTOSKRNL] - Raise the IRQL when
enumerating device lists so it doesn't get edited mid-listing - Don't
hardcode the pointer size when checking the buffer size

Uhm... raising the IRQL is not a synchronization mechanism. Should there be
a spinlock involved?


On 2015-12-23 12:26, gedmurphy(a)svn.reactos.org wrote:
>   Author: gedmurphy
>  Date: Wed Dec 23 11:26:28 2015
>  New Revision: 70408
>  
>  URL: http://svn.reactos.org/svn/reactos?rev=70408&view=rev
>  Log:
>  [NTOSKRNL]
>  - Raise the IRQL when enumerating device lists so it doesn't get 
>  edited mid-listing
>  - Don't hardcode the pointer size when checking the buffer size
>  
>  Modified:
>      trunk/reactos/ntoskrnl/io/iomgr/device.c
>  
>  Modified: trunk/reactos/ntoskrnl/io/iomgr/device.c
>  URL: 
>  http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/io/iomgr/dev
>  ice.c?rev=70408&r1=70407&r2=70408&view=diff
>  
============================================================================
==
>   ---
> trunk/reactos/ntoskrnl/io/iomgr/device.c	[iso-8859-1] (original)
>  +++ trunk/reactos/ntoskrnl/io/iomgr/device.c	[iso-8859-1] Wed Dec 23 
11:26:28 2015
>   @@ -1088,6 +1088,10 @@
>   {
>       ULONG ActualDevices = 1;
>       PDEVICE_OBJECT CurrentDevice = DriverObject->DeviceObject;
>  +    KIRQL OldIrql;
>  +
>  +    /* Raise to dispatch level */
>  +    KeRaiseIrql(DISPATCH_LEVEL, &OldIrql);
>   
>       /* Find out how many devices we'll enumerate */
>       while ((CurrentDevice = CurrentDevice->NextDevice))
>  ActualDevices++; @@ -1099,13 +1103,14 @@
>       *ActualNumberDeviceObjects = ActualDevices;
>   
>       /* Check if we can support so many */
>  -    if ((ActualDevices * 4) > DeviceObjectListSize)
>  +    if ((ActualDevices * sizeof(PDEVICE_OBJECT)) >
>  + DeviceObjectListSize)
>       {
>           /* Fail because the buffer was too small */
>  +        KeLowerIrql(OldIrql);
>           return STATUS_BUFFER_TOO_SMALL;
>       }
>   
>  -    /* Check if the caller only wanted the size */
>  +    /* Check if the caller wanted the device list */
>       if (DeviceObjectList)
>       {
>           /* Loop through all the devices */ @@ -1123,6 +1128,9 @@
>               DeviceObjectList++;
>           }
>       }
>  +
>  +    /* Return back to previous IRQL */
>  +    KeLowerIrql(OldIrql);
>   
>       /* Return the status */
>       return STATUS_SUCCESS;
>  
>   

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