Memory De-Allocation crash.

NTDEV
1

Hi,

I am de-allocating memory for a structure(and its buffers) that where allocated beforehand but crash happens when i am doing trying to do this.

After some testing i noticed that when i deallocate the structers by getting the pointer to the structures from an entry list its crashing but when i use the pointer that they where created with it works fine.

here is the code:

//Allocation
NdisAllocateMemoryWithTag(&pPacket, sizeof(PACKET),‘oiuN’)
NdisAllocateMemoryWithTag(&pPacket->aStructA,LookaheadBufferSize, ‘oiuN’);
NdisAllocateMemoryWithTag(&pPacket->aStructA,HeaderBufferSize, ‘oiuN’);

//De-allocation code
pEnt = RemoveHeadList(&masterstruct->Packets);
IP = (PPACKET) pEnt;
if(IP!=NULL)
{
NdisFreeMemory(IP->aStructA,0,0);
NdisFreeMemory(IP->aStructB,0,0);
NdisFreeMemory(IP, 0, 0);
}

(pPacket and IP is a pointer to a custom structure with some NDIS_BUFFERS and a LIST_ENTRY link)

( i am doing all this from within the ReceiveHandler function entry point)

any ideas??

Thanks !!

2

Firstly,

IP = (PPACKET) pEnt;

is going to give you garbage. pEnt is a pointer to LIST_ENTRY
struct. In the fluke case where the LIST_ENTRY in your PACKET struct
just happens to be the first element then

IP = (PPACKET) pEnt->fLink;

might work. However, you need to check out the CONTAINING_RECORD
macro and scan the WDK samples for an example of its use.

Mark.

At 11:53 24/01/2011, xxxxx@hotmail.com wrote:

Hi,

I am de-allocating memory for a structure(and its buffers) that
where allocated beforehand but crash happens when i am doing trying
to do this.

After some testing i noticed that when i deallocate the structers
by getting the pointer to the structures from an entry list its
crashing but when i use the pointer that they where created with it
works fine.

here is the code:

//Allocation
NdisAllocateMemoryWithTag(&pPacket, sizeof(PACKET),‘oiuN’)
NdisAllocateMemoryWithTag(&pPacket->aStructA,LookaheadBufferSize, ‘oiuN’);
NdisAllocateMemoryWithTag(&pPacket->aStructA,HeaderBufferSize, ‘oiuN’);

//De-allocation code
pEnt = RemoveHeadList(&masterstruct->Packets);
IP = (PPACKET) pEnt;
if(IP!=NULL)
{
NdisFreeMemory(IP->aStructA,0,0);
NdisFreeMemory(IP->aStructB,0,0);
NdisFreeMemory(IP, 0, 0);
}

(pPacket and IP is a pointer to a custom structure with some
NDIS_BUFFERS and a LIST_ENTRY link)

( i am doing all this from within the ReceiveHandler function entry point)

any ideas??

Thanks !!

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3

Thx the problem was when i was casting as you said.
when i used he macro it worked.

what is i cant understand is that when i read the data it semed valid (i.E it was casting good since i read the data and it was valid so the ptr returned must be have been good)

4

First, RemoveHeadList NEVER returns NULL. Before you call it, you need to check if the list is not empty: IsListEmpty()

5

xxxxx@hotmail.com wrote:

Hi,

I am de-allocating memory for a structure(and its buffers) that where allocated beforehand but crash happens when i am doing trying to do this.

After some testing i noticed that when i deallocate the structers by getting the pointer to the structures from an entry list its crashing but when i use the pointer that they where created with it works fine.

here is the code:

//Allocation
NdisAllocateMemoryWithTag(&pPacket, sizeof(PACKET),‘oiuN’)
NdisAllocateMemoryWithTag(&pPacket->aStructA,LookaheadBufferSize, ‘oiuN’);
NdisAllocateMemoryWithTag(&pPacket->aStructA,HeaderBufferSize, ‘oiuN’);

You can see there’s a typo there, right? If you cut-and-pasted that
from the actual code, you need to change the third one to aStructB, not
aStructA. If you retyped this character by character, then who knows.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.