Re: [PATCH v5 6/6] x86/microcode/AMD: Check the equivalence table size when scanning it

Borislav Petkov
2018-04-30T09:06:19Z

On Mon, Apr 23, 2018 at 11:34:11PM +0200, Maciej S. Szmigiero wrote:
> Currently, the code scanning the CPU equivalence table read from a
> microcode container file assumes that it actually contains a terminating
> zero entry.
> Let's check also the size of this table to make sure that we don't read
> past it in case it actually doesn't.

...

> @@ -697,6 +706,7 @@ static unsigned int install_equiv_cpu_table(const u8 *buf, size_t buf_size)
> }
>
> memcpy(equiv_cpu_table, buf + CONTAINER_HDR_SZ, equiv_tbl_len);
> + equiv_cpu_table_entries = equiv_tbl_len / sizeof(struct equiv_cpu_entry);
>
> return equiv_tbl_len;

Instead of adding yet another global var which needs handling too,
and touching so many places, just do all checks and preparations in
install_equiv_cpu_table() so that the rest of the code can get what it
expects: terminating zero entry and proper size.

Thx.

--
Regards/Gruss,
Boris.

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