Messages in this thread | | | Date | Mon, 12 Mar 2018 14:48:53 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v2] x86/microcode/AMD: check microcode file sanity before loading it |
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On Mon, Mar 12, 2018 at 02:32:30PM +0100, Maciej S. Szmigiero wrote: > "microcode_amd.bin" in linux-firmware.
That is the microcode container for all families < 0x15. And it *happens* to have 18 entries.
So purely arbitrary:
Equivalence table (magic: AMD, type: 0, length: 288 (0x120)) ============================================================ | inst_cpu | err_msk | err_cmp | eq_cpu | res | ========================================================== | 0x00100f80 | 0x00000000 | 0x00000000 | 0x1080 | 0x0000 | | 0x00100f81 | 0x00000000 | 0x00000000 | 0x1081 | 0x0000 | | 0x00100f62 | 0x00000000 | 0x00000000 | 0x1062 | 0x0000 | | 0x00100f23 | 0x00000000 | 0x00000000 | 0x1022 | 0x0000 | | 0x00100f43 | 0x00000000 | 0x00000000 | 0x1043 | 0x0000 | | 0x00100f91 | 0x00000000 | 0x00000000 | 0x1081 | 0x0000 | | 0x00100f2a | 0x00000000 | 0x00000000 | 0x1020 | 0x0000 | | 0x00100f63 | 0x00000000 | 0x00000000 | 0x1043 | 0x0000 | | 0x00100f42 | 0x00000000 | 0x00000000 | 0x1041 | 0x0000 | | 0x00300f10 | 0x00000000 | 0x00000000 | 0x3010 | 0x0000 | | 0x00200f31 | 0x00000000 | 0x00000000 | 0x2031 | 0x0000 | | 0x00100f52 | 0x00000000 | 0x00000000 | 0x1041 | 0x0000 | | 0x00100fa0 | 0x00000000 | 0x00000000 | 0x10a0 | 0x0000 | | 0x00100f53 | 0x00000000 | 0x00000000 | 0x1043 | 0x0000 | | 0x00100f22 | 0x00000000 | 0x00000000 | 0x1022 | 0x0000 | | 0x00500f10 | 0x00000000 | 0x00000000 | 0x5010 | 0x0000 | | 0x00500f20 | 0x00000000 | 0x00000000 | 0x5020 | 0x0000 | | 0x00000000 | 0x00000000 | 0x00000000 | 0x0000 | 0x0000 |
> There is no problem raising this value in that (future) case. > As I wrote previously, currently the maximum used count is 18.
There is a problem because not everyone can upgrade their kernels like you. Distros and big deployments can't just up and update their kernels at a whim just because you imposed an arbitrary limit which you determined would be ok.
> Not really, since even in the existing code CONTAINER_HDR_SZ (12) gets > added to this size, then the sum is cast to a (signed) int. > If this value is negative then the file get rejected.
That is a bug in install_equiv_cpu_table() - it should return unsigned int.
> It can be changed to the current maximum across sizes for particular
What is the "current maximum across sizes"?
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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