From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 51C932857C4; Mon, 19 May 2025 18:24:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747679073; cv=none; b=BBScI/T/gM0lbdH7laIsjOOPZYM/evpAA29rd7ib7dJ7HT38h+Yd6Z3e1tJ5cCt5GpBfan3AkRnlvGwcU3/8fd/l69sIRihTU6lXRFwFKBIE6nX/e8HB0qO3rlU900OfeDT3go6B49UCGzE1TOPUGRM+xApRDiKhS3bkX8JBbfA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747679073; c=relaxed/simple; bh=1KXAzjMSe/ri37+m07NJN/eRVwd604m2Fdfu1XxKbZE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aNNzoJFQWkMR+zM0KwsHm73HajmQidWVtkrt/AS7+bhLEi4aSuwPm7V+R6uz9EGR8s7im3CkIjqueznlD/AeH5amOq2kl5AL03QsA9xhYXNk4ozILaMm7drBHdFTUws7CYYgszpPGoQKwHjn3gU2qBvKjK+sQjopQcnJNAtwbok= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=l+LWGzHw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="l+LWGzHw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A402CC4CEE4; Mon, 19 May 2025 18:24:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747679073; bh=1KXAzjMSe/ri37+m07NJN/eRVwd604m2Fdfu1XxKbZE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=l+LWGzHwPLt9tuDO2OcldxtSI5ZY3J8HPzrk0cPNCGCz6dcAEu2vQfDlzMOAjU1Ls VjTCWQlsOiSydSXIjojXyUgFyOijsOk4u4Sy9ZHQm58p4drcySd3SdMnf2YsSv3/Mv AHRCjp4VqAzvufFY3qJgxWtYWybUTut7PVTjp7CdNAqvfMCzBQhE0qAUzFtHw+z9ZJ kAxVQ0HRFoWe0RRjMUNqDiNrXBhB+8HjRPNNLRYLL/PrXzxxsFsEtYOVpKy9A6GDpG hB44nxs98KijGU7OowwfGML52gsiHF7vPf8rILBu6vgC+2SvmiqkSXP/7bxzY0vFjv NvluuWmqBIrTA== Date: Mon, 19 May 2025 21:24:29 +0300 From: Jarkko Sakkinen To: Elena Reshetova Cc: dave.hansen@intel.com, seanjc@google.com, kai.huang@intel.com, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, asit.k.mallick@intel.com, vincent.r.scarlata@intel.com, chongc@google.com, erdemaktas@google.com, vannapurve@google.com, dionnaglaze@google.com, bondarn@google.com, scott.raynor@intel.com Subject: Re: [PATCH v5 4/5] x86/sgx: Implement ENCLS[EUPDATESVN] Message-ID: References: <20250519072603.328429-1-elena.reshetova@intel.com> <20250519072603.328429-5-elena.reshetova@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250519072603.328429-5-elena.reshetova@intel.com> On Mon, May 19, 2025 at 10:24:30AM +0300, Elena Reshetova wrote: > The SGX attestation architecture assumes a compromise > of all running enclaves and cryptographic assets > (like internal SGX encryption keys) whenever a microcode > update affects SGX. To mitigate the impact of this presumed > compromise, a new supervisor SGX instruction: ENCLS[EUPDATESVN], > is introduced to update SGX microcode version and generate > new cryptographic assets in runtime after SGX microcode update. > > EUPDATESVN requires that SGX memory to be marked as "unused" > before it will succeed. This ensures that no compromised enclave > can survive the process and provides an opportunity to generate > new cryptographic assets. > > Add the method to perform ENCLS[EUPDATESVN]. > > Signed-off-by: Elena Reshetova > --- > arch/x86/kernel/cpu/sgx/encls.h | 5 +++ > arch/x86/kernel/cpu/sgx/main.c | 57 +++++++++++++++++++++++++++++++++ > 2 files changed, 62 insertions(+) > > diff --git a/arch/x86/kernel/cpu/sgx/encls.h b/arch/x86/kernel/cpu/sgx/encls.h > index 99004b02e2ed..d9160c89a93d 100644 > --- a/arch/x86/kernel/cpu/sgx/encls.h > +++ b/arch/x86/kernel/cpu/sgx/encls.h > @@ -233,4 +233,9 @@ static inline int __eaug(struct sgx_pageinfo *pginfo, void *addr) > return __encls_2(EAUG, pginfo, addr); > } > > +/* Attempt to update CPUSVN at runtime. */ > +static inline int __eupdatesvn(void) > +{ > + return __encls_ret_1(EUPDATESVN, ""); > +} > #endif /* _X86_ENCLS_H */ > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index 80d565e6f2ad..fd71e2ddca59 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -15,6 +15,7 @@ > #include > #include > #include > +#include > #include "driver.h" > #include "encl.h" > #include "encls.h" > @@ -917,6 +918,62 @@ EXPORT_SYMBOL_GPL(sgx_set_attribute); > /* Counter to count the active SGX users */ > static atomic64_t sgx_usage_count; > > +/** > + * sgx_updatesvn() - Attempt to call ENCLS[EUPDATESVN] > + * If EPC is empty, this instruction attempts to update CPUSVN to the > + * currently loaded microcode update SVN and generate new > + * cryptographic assets.sgx_updatesvn() Most of the time, there will Is there something wrong here in the text? It looks malformed. > + * be no update and that's OK. > + * > + * Return: > + * 0: Success, not supported or run out of entropy > + */ > +static int sgx_update_svn(void) > +{ > + int ret; > + > + /* > + * If EUPDATESVN is not available, it is ok to > + * silently skip it to comply with legacy behavior. > + */ > + if (!X86_FEATURE_SGX_EUPDATESVN) > + return 0; > + > + for (int i = 0; i < RDRAND_RETRY_LOOPS; i++) { > + ret = __eupdatesvn(); > + > + /* Stop on success or unexpected errors: */ > + if (ret != SGX_INSUFFICIENT_ENTROPY) > + break; > + } > + > + /* > + * SVN either was up-to-date or SVN update failed due > + * to lack of entropy. In both cases, we want to return > + * 0 in order not to break sgx_(vepc_)open. We dont expect > + * SGX_INSUFFICIENT_ENTROPY error unless underlying RDSEED > + * is under heavy pressure. > + */ > + if ((ret == SGX_NO_UPDATE) || (ret == SGX_INSUFFICIENT_ENTROPY)) if (ret == SGX_NO_UPDATE || ret == SGX_INSUFFICIENT_ENTROPY) > + return 0; > + > + if (!ret) { > + /* > + * SVN successfully updated. > + * Let users know when the update was successful. > + */ This comment is like as useless as an inline comment can ever possibly be. Please, remove it. > + pr_info("SVN updated successfully\n"); Let's not add this either in the scope of this patch set. > + return 0; > + } Since you parse error codes already, I don't understand why deal with the success case in the middle of doing that. More consistent would be (not also the use of unlikely()): if (ret == SGX_NO_UPDATE || ret == SGX_INSUFFICIENT_ENTROPY) return 0; /* * EUPDATESVN was called when EPC is empty, all other error * codes are unexpected. */ if (unlikely(ret)) { ENCLS_WARN(ret, "EUPDATESVN"); return ret; } return 0; } This is how I would rewrite the tail of this function. BR, Jarkko