Re: [PATCH v2] x86/microcode/AMD: check microcode file sanity before loading it

[Borislav Petkov]

On Mon, Mar 12, 2018 at 01:56:59PM +0100, Maciej S. Szmigiero wrote:
> The equivalent CPU table is allocated using vmalloc() so it is nice
> when the maximum size is an integer multiple of the page size.

Arbitrary.

> Since the maximum entry count in current microcode files is 18 the

Where did you dream up that 18?

> maximum size of 256 entries (or one page) gives us plenty of headroom.

Arbitrary.

> Also, looking in the past, there probably won't be more than 256 AMD CPU
> types in one CPU family.

Wrong.

The only limitation on the equivalence table size we have is the 32-bit
unsigned length field at offset 8 in the equivalence table header.

> This limit is an absolute upper cap of a patch size.

More dreamt up crap.

See verify_patch_size() for the actual patch sizes.

-- 
Regards/Gruss,
    Boris.

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