linux-kernel - RE: [Patch v3 05/14] x86/mm: Handle decryption/re-encryption of bss

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 18 Nov 2022 02:59:48 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Tom Lendacky <thomas.lendacky@....com>,
        "hpa@...or.com" <hpa@...or.com>, KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
        "robh@...nel.org" <robh@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "hch@...radead.org" <hch@...radead.org>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "isaku.yamahata@...el.com" <isaku.yamahata@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "jane.chu@...cle.com" <jane.chu@...cle.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
Subject: RE: [Patch v3 05/14] x86/mm: Handle decryption/re-encryption of
 bss_decrypted consistently

From: Tom Lendacky <thomas.lendacky@....com> Sent: Wednesday, November 16, 2022 1:16 PM
> 
> On 11/16/22 14:35, Tom Lendacky wrote:
> > On 11/16/22 12:41, Michael Kelley wrote:
> >> Current code in sme_postprocess_startup() decrypts the bss_decrypted
> >> section when sme_me_mask is non-zero.  But code in
> >> mem_encrypt_free_decrytped_mem() re-encrypts the unused portion based
> >> on CC_ATTR_MEM_ENCRYPT.  In a Hyper-V guest VM using vTOM, these
> >> conditions are not equivalent as sme_me_mask is always zero when
> >> using vTOM.  Consequently, mem_encrypt_free_decrypted_mem() attempts
> >> to re-encrypt memory that was never decrypted.
> >>
> >> Fix this in mem_encrypt_free_decrypted_mem() by conditioning the
> >> re-encryption on the same test for non-zero sme_me_mask.  Hyper-V
> >> guests using vTOM don't need the bss_decrypted section to be
> >> decrypted, so skipping the decryption/re-encryption doesn't cause
> >> a problem.
> >>
> >> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
> 
> Meant to add this in the previous reply...
> 
> With the change to use sme_me_mask directly
> 
> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> 

Thanks for the reviews.  And I see your point about sme_me_mask.  I had
not previously noticed that it is defined in the module, so no need to use
a getter function.

Michael