Problem while opening a shared file.

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Hello, Sorry for the basic question. I need to create a file for write access in kernel mode and and allow other thread to read it, this can happen simultaneously. so This what I do when creating the file.

C++

    status = ZwCreateFile(&hfile,
                        GENERIC_WRITE,
                        &oa,
                        &iostatus,
                        NULL,
                        FILE_ATTRIBUTE_NORMAL,
                        FILE_SHARE_READ,
                        FILE_OVERWRITE_IF,
                        FILE_SYNCHRONOUS_IO_NONALERT,
                        NULL,
                        0);

}

works well, the file is created for write and later when I try to create another handle to read it I always get "STATUS_SHARING_VIOLATION"
here is how I do it.

C++

ntstatus = ZwCreateFile(&OriFileHandle,
							FILE_READ_DATA,
							&objOriAttr,
							&ioOriStatusBlock,
							NULL,
							FILE_ATTRIBUTE_NORMAL,
							FILE_SHARE_READ,
							FILE_OPEN,
							FILE_SYNCHRONOUS_IO_NONALERT | FILE_NON_DIRECTORY_FILE,
							NULL,
							0);

Can anybody tell me what is it that I am doing wrong?

What I have tried:

I already read about ZwCreatefile and how to share a file for access by other thread but I am still getting that error.

Posted 22-Mar-16 16:51pm

Wshwilfried

Updated 4-Apr-16 7:33am

PIEBALDconsult

v2

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Wshwilfried 22-Mar-16 23:58pm

In my second call to ZwCreateFile I set the desired access to SYNCHRONIZE and it worked. Can anyone explain why? I thought since My goal is to simultaneously read the file I had to provide FILE_READ_DATA or GENERIC_READ.

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bling · Accepted Answer · 2016-04-04T07:33:00

It looks like you are mixing access flags with other types of flags. Also, you omit FILE_SHARE_WRITE in the second ZwCreateFile.

Try this:

C++

ntstatus = ZwCreateFile(&OriFileHandle,
							GENERIC_READ,
							&objOriAttr,
							&ioOriStatusBlock,
							NULL,
							FILE_ATTRIBUTE_NORMAL,
							FILE_SHARE_WRITE,
							FILE_OPEN,
							FILE_SYNCHRONOUS_IO_NONALERT | FILE_NON_DIRECTORY_FILE, // I've never used these.
							NULL,
							0);