linux-kernel - RE: [PATCH v3 3/3] x86/hyperv: Make encrypted/decrypted changes safe for load_unaligned

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Message-ID:
 <SN6PR02MB415728EA80420231DF35BB36D46F2@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Fri, 12 Jan 2024 03:19:55 +0000
From: Michael Kelley <mhklinux@...look.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"ardb@...nel.org" <ardb@...nel.org>, "hch@...radead.org" <hch@...radead.org>,
	"Lutomirski, Andy" <luto@...nel.org>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>, "thomas.lendacky@....com"
	<thomas.lendacky@....com>, "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"mingo@...hat.com" <mingo@...hat.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"Cui, Dexuan" <decui@...rosoft.com>, "urezki@...il.com" <urezki@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "hpa@...or.com" <hpa@...or.com>,
	"peterz@...radead.org" <peterz@...radead.org>, "wei.liu@...nel.org"
	<wei.liu@...nel.org>, "bp@...en8.de" <bp@...en8.de>, "Rodel, Jorg"
	<jroedel@...e.de>, "sathyanarayanan.kuppuswamy@...ux.intel.com"
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, "lstoakes@...il.com"
	<lstoakes@...il.com>, "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH v3 3/3] x86/hyperv: Make encrypted/decrypted changes safe
 for load_unaligned_zeropad()

From: Edgecombe, Rick P <rick.p.edgecombe@...el.com> Sent: Thursday, January 11, 2024 4:27 PM
> 
> On Fri, 2024-01-05 at 10:30 -0800, mhkelley58@...il.com wrote:
> >   * hv_vtom_set_host_visibility - Set specified memory visible to host.
> >   *
> > @@ -521,7 +547,7 @@ static bool hv_vtom_set_host_visibility(unsigned long kbuffer, int pagecount, bo
> >
> >         pfn_array = kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
> >         if (!pfn_array)
> > -               return false;
> > +               goto err_set_memory_p;
> >
> 
> If kmalloc() fails here, and set_memory_p() succeeds below, then
> hv_vtom_set_host_visibility() returns true, but skips all the
> hv_mark_gpa_visibility() work. Shouldn't it return false?

Ooops.  Yes.  If the kmalloc() fails, need to set "result" to false before
doing the goto.  Will fix in the next version.

Michael