linux-kernel - Re: [patch 2/8] x86/fpu: Prevent state corruption in __fpu__restore

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Date:   Wed, 02 Jun 2021 16:46:04 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        syzbot+2067e764dbcd10721e2e@...kaller.appspotmail.com,
        stable@...r.kernel.org
Subject: Re: [patch 2/8] x86/fpu: Prevent state corruption in __fpu__restore_sig()

On Wed, Jun 02 2021 at 15:12, Borislav Petkov wrote:
>>  /* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
>> -int validate_user_xstate_header(const struct xstate_header *hdr)
>> +static int validate_user_xstate_header(const struct xstate_header *hdr)
>
> Can't do that yet - that one is still called from regset.c:
>
> arch/x86/kernel/fpu/regset.c: In function ‘xstateregs_set’:
> arch/x86/kernel/fpu/regset.c:135:10: error: implicit declaration of function ‘validate_user_xstate_header’ [-Werror=implicit-function-declaration]
>   135 |    ret = validate_user_xstate_header(&xsave->header);
>       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: some warnings being treated as errors
>
> Maybe after the 5th patch which kills that usage too.

Gah, yes. I had the patches ordered differently and then failed to do a
full step by step recompile after reshuffling them. Fixed localy.

Thanks,

        tglx