linux-kernel - Re: [PATCH 15/23] x86/fpu: Add sanity checks for XFD

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Date:   Mon, 25 Oct 2021 22:15:03 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>,
        "Chang S. Bae" <chang.seok.bae@...el.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        dave.hansen@...ux.intel.com, arjan@...ux.intel.com,
        ravi.v.shankar@...el.com
Subject: Re: [PATCH 15/23] x86/fpu: Add sanity checks for XFD

On Mon, Oct 25 2021 at 10:11, Borislav Petkov wrote:

> On Thu, Oct 21, 2021 at 03:55:19PM -0700, Chang S. Bae wrote:
>> @@ -217,12 +240,15 @@ static inline int xrstor_from_user_sigframe(struct xregs_state __user *buf, u64
>>   * Restore xstate from kernel space xsave area, return an error code instead of
>>   * an exception.
>>   */
>> -static inline int os_xrstor_safe(struct xregs_state *xstate, u64 mask)
>> +static inline int os_xrstor_safe(struct fpstate *fpstate, u64 mask)
>>  {
>> +	struct xregs_state *xstate = &fpstate->regs.xsave;
>>  	u32 lmask = mask;
>>  	u32 hmask = mask >> 32;
>>  	int err;
>>  
>> +	/* Must enforce XFD update here */
>> +
>
> <--- something's missing here?

That comment is replaced in the next patch which adds the actual XFD
update. I added it as a reminder. Could probably go away.

Thanks,

        tglx