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Date:   Tue, 27 Oct 2020 03:52:22 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Borislav Petkov <bp@alien8.de>, x86@kernel.org,
        linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        Jethro Beekman <jethro@fortanix.com>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Chunyang Hui <sanqian.hcy@antfin.com>,
        Jordan Hand <jorhand@linux.microsoft.com>,
        Nathaniel McCallum <npmccallum@redhat.com>,
        Seth Moore <sethmo@google.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com,
        asapek@google.com, cedric.xing@intel.com, chenalexchen@google.com,
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        haitao.huang@intel.com, josh@joshtriplett.org, kai.huang@intel.com,
        kai.svahn@intel.com, kmoy@google.com, ludloff@google.com,
        luto@kernel.org, nhorman@redhat.com, puiterwijk@redhat.com,
        rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com
Subject: Re: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver
Message-ID: <20201027015222.GC20485@linux.intel.com>
References: <20200617220844.57423-1-jarkko.sakkinen@linux.intel.com>
 <20200617220844.57423-12-jarkko.sakkinen@linux.intel.com>
 <20200626153400.GE27151@zn.tnic>
 <1ada871a-2350-1007-c625-a00bdb0d439b@intel.com>
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Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
Precedence: bulk

On Mon, Oct 26, 2020 at 02:26:13PM -0700, Dave Hansen wrote:
> On 6/26/20 8:34 AM, Borislav Petkov wrote:
> >> +	if (!(atomic_read(&encl->flags) & SGX_ENCL_CREATED))
> >> +		return -EINVAL;
> >> +
> >> +	if (copy_from_user(&addp, arg, sizeof(addp)))
> >> +		return -EFAULT;
> >> +
> >> +	if (!IS_ALIGNED(addp.offset, PAGE_SIZE) ||
> >> +	    !IS_ALIGNED(addp.src, PAGE_SIZE))
> >> +		return -EINVAL;
> >> +
> >> +	if (!(access_ok(addp.src, PAGE_SIZE)))
> >> +		return -EFAULT;
> >> +
> >> +	if (addp.length & (PAGE_SIZE - 1))
> >> +		return -EINVAL;
> > How many pages are allowed? Unlimited? I'm hoping some limits are
> > checked somewhere...
> 
> What were you concerned about here?  Was it how long the syscall could
> take, or that one user could exhaust all the enclave memory in one call?
> 
> Some later versions of this patch have a 1MB limit per to reduce how
> long each SGX_IOC_ENCLAVE_ADD_PAGES call spends in the kernel.  But, I'm
> not _sure_ that's what you were intending.

The loop does check for pending signals, i.e. it is possible to
interrupt it.

/Jarkko