linux-kernel - Re: [PATCH v5 4/6] x86/microcode/AMD: Check microcode container data in the late loader

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Message-ID: <20180501084317.GC31863@pd.tnic>
Date:   Tue, 1 May 2018 10:43:17 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 4/6] x86/microcode/AMD: Check microcode container data
 in the late loader

On Tue, May 01, 2018 at 12:27:51AM +0200, Maciej S. Szmigiero wrote:
> 1) -EINVAL maps to a valid return value of 4294967274 bytes.
> We have a different behavior for invalid data in the container file
> (including too large lengths) than for grave errors like a failed memory
> allocation.

WTF?

> 2) This function single caller (__load_microcode_amd()) normalized any
> error that verify_and_add_patch() returned to UCODE_ERROR anyway,

So?

> 3) The existing code uses a convention that zero return value means
> 'terminate processing' for the parse_container() function in the early
> loader which normally returns a 'bytes consumed' value, as this function
> does.

parse_container() could very well change its convention to return
negative on error and positive value if the loop is supposed to skip
bytes.

-- 
Regards/Gruss,
    Boris.

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