From: Chao Peng <chao.p.peng@linux.intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-api@vger.kernel.org, qemu-devel@nongnu.org,
Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Hugh Dickins <hughd@google.com>, Jeff Layton <jlayton@kernel.org>,
"J . Bruce Fields" <bfields@fieldses.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Rapoport <rppt@kernel.org>,
Steven Price <steven.price@arm.com>,
"Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
Vlastimil Babka <vbabka@suse.cz>,
Vishal Annapurve <vannapurve@google.com>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com,
ak@linux.intel.com, david@redhat.com
Subject: Re: [PATCH v5 06/13] KVM: Use kvm_userspace_memory_region_ext
Date: Fri, 8 Apr 2022 21:58:37 +0800 [thread overview]
Message-ID: <20220408135837.GE57095@chaop.bj.intel.com> (raw)
In-Reply-To: <YkI2Lyv9SJaGPDz+@google.com>
On Mon, Mar 28, 2022 at 10:26:55PM +0000, Sean Christopherson wrote:
> On Thu, Mar 10, 2022, Chao Peng wrote:
> > @@ -4476,14 +4477,23 @@ static long kvm_vm_ioctl(struct file *filp,
> > break;
> > }
> > case KVM_SET_USER_MEMORY_REGION: {
> > - struct kvm_userspace_memory_region kvm_userspace_mem;
> > + struct kvm_userspace_memory_region_ext region_ext;
>
> It's probably a good idea to zero initialize the full region to avoid consuming
> garbage stack data if there's a bug and an _ext field is accessed without first
> checking KVM_MEM_PRIVATE. I'm usually opposed to unnecessary initialization, but
> this seems like something we could screw up quite easily.
>
> > r = -EFAULT;
> > - if (copy_from_user(&kvm_userspace_mem, argp,
> > - sizeof(kvm_userspace_mem)))
> > + if (copy_from_user(®ion_ext, argp,
> > + sizeof(struct kvm_userspace_memory_region)))
> > goto out;
> > + if (region_ext.region.flags & KVM_MEM_PRIVATE) {
> > + int offset = offsetof(
> > + struct kvm_userspace_memory_region_ext,
> > + private_offset);
> > + if (copy_from_user(®ion_ext.private_offset,
> > + argp + offset,
> > + sizeof(region_ext) - offset))
>
> In this patch, KVM_MEM_PRIVATE should result in an -EINVAL as it's not yet
> supported. Copying the _ext on KVM_MEM_PRIVATE belongs in the "Expose KVM_MEM_PRIVATE"
> patch.
Agreed.
>
> Mechnically, what about first reading flags via get_user(), and then doing a single
> copy_from_user()? It's technically more work in the common case, and requires an
> extra check to guard against TOCTOU attacks, but this isn't a fast path by any means
> and IMO the end result makes it easier to understand the relationship between
> KVM_MEM_PRIVATE and the two different structs.
Will use this code, thanks for typing.
Chao
>
> E.g.
>
> case KVM_SET_USER_MEMORY_REGION: {
> struct kvm_user_mem_region region;
> unsigned long size;
> u32 flags;
>
> memset(®ion, 0, sizeof(region));
>
> r = -EFAULT;
> if (get_user(flags, (u32 __user *)(argp + offsetof(typeof(region), flags))))
> goto out;
>
> if (flags & KVM_MEM_PRIVATE)
> size = sizeof(struct kvm_userspace_memory_region_ext);
> else
> size = sizeof(struct kvm_userspace_memory_region);
> if (copy_from_user(®ion, argp, size))
> goto out;
>
> r = -EINVAL;
> if ((flags ^ region.flags) & KVM_MEM_PRIVATE)
> goto out;
>
> r = kvm_vm_ioctl_set_memory_region(kvm, ®ion);
> break;
> }
>
> > + goto out;
> > + }
> >
> > - r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem);
> > + r = kvm_vm_ioctl_set_memory_region(kvm, ®ion_ext);
> > break;
> > }
> > case KVM_GET_DIRTY_LOG: {
> > --
> > 2.17.1
> >
next prev parent reply other threads:[~2022-04-08 13:58 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-10 14:08 [PATCH v5 00/13] KVM: mm: fd-based approach for supporting KVM guest private memory Chao Peng
2022-03-10 14:08 ` [PATCH v5 01/13] mm/memfd: Introduce MFD_INACCESSIBLE flag Chao Peng
2022-04-11 15:10 ` Kirill A. Shutemov
2022-04-12 13:11 ` Chao Peng
2022-04-23 5:43 ` Vishal Annapurve
2022-04-24 8:15 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 02/13] mm: Introduce memfile_notifier Chao Peng
2022-03-29 18:45 ` Sean Christopherson
2022-04-08 12:54 ` Chao Peng
2022-04-12 14:36 ` Hillf Danton
2022-04-13 6:47 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 03/13] mm/shmem: Support memfile_notifier Chao Peng
2022-03-10 23:08 ` Dave Chinner
2022-03-11 8:42 ` Chao Peng
2022-04-11 15:26 ` Kirill A. Shutemov
2022-04-12 13:12 ` Chao Peng
2022-04-19 22:40 ` Vishal Annapurve
2022-04-20 3:24 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 04/13] mm/shmem: Restrict MFD_INACCESSIBLE memory against RLIMIT_MEMLOCK Chao Peng
2022-04-07 16:05 ` Sean Christopherson
2022-04-07 17:09 ` Andy Lutomirski
2022-04-08 17:56 ` Sean Christopherson
2022-04-08 18:54 ` David Hildenbrand
2022-04-12 14:36 ` Jason Gunthorpe
2022-04-12 21:27 ` Andy Lutomirski
2022-04-13 16:30 ` David Hildenbrand
2022-04-13 16:24 ` David Hildenbrand
2022-04-13 17:52 ` Jason Gunthorpe
2022-04-25 14:07 ` David Hildenbrand
2022-04-08 13:02 ` Chao Peng
2022-04-11 15:34 ` Kirill A. Shutemov
2022-04-12 5:14 ` Hugh Dickins
2022-04-11 15:32 ` Kirill A. Shutemov
2022-04-12 13:39 ` Chao Peng
2022-04-12 19:28 ` Kirill A. Shutemov
2022-04-13 9:15 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 05/13] KVM: Extend the memslot to support fd-based private memory Chao Peng
2022-03-28 21:27 ` Sean Christopherson
2022-04-08 13:21 ` Chao Peng
2022-03-28 21:56 ` Sean Christopherson
2022-04-08 13:46 ` Chao Peng
2022-04-08 17:45 ` Sean Christopherson
2022-03-10 14:09 ` [PATCH v5 06/13] KVM: Use kvm_userspace_memory_region_ext Chao Peng
2022-03-28 22:26 ` Sean Christopherson
2022-04-08 13:58 ` Chao Peng [this message]
2022-03-10 14:09 ` [PATCH v5 07/13] KVM: Add KVM_EXIT_MEMORY_ERROR exit Chao Peng
2022-03-28 22:33 ` Sean Christopherson
2022-04-08 13:59 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 08/13] KVM: Use memfile_pfn_ops to obtain pfn for private pages Chao Peng
2022-03-28 23:56 ` Sean Christopherson
2022-04-08 14:07 ` Chao Peng
2022-04-28 12:37 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 09/13] KVM: Handle page fault for private memory Chao Peng
2022-03-29 1:07 ` Sean Christopherson
2022-04-12 12:10 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 10/13] KVM: Register private memslot to memory backing store Chao Peng
2022-03-29 19:01 ` Sean Christopherson
2022-04-12 12:40 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 11/13] KVM: Zap existing KVM mappings when pages changed in the private fd Chao Peng
2022-03-29 19:23 ` Sean Christopherson
2022-04-12 12:43 ` Chao Peng
2022-04-05 23:45 ` Michael Roth
2022-04-08 3:06 ` Sean Christopherson
2022-04-19 22:43 ` Vishal Annapurve
2022-04-20 3:17 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 12/13] KVM: Expose KVM_MEM_PRIVATE Chao Peng
2022-03-29 19:13 ` Sean Christopherson
2022-04-12 12:56 ` Chao Peng
2022-03-10 14:09 ` [PATCH v5 13/13] memfd_create.2: Describe MFD_INACCESSIBLE flag Chao Peng
2022-03-24 15:51 ` [PATCH v5 00/13] KVM: mm: fd-based approach for supporting KVM guest private memory Quentin Perret
2022-03-28 17:13 ` Sean Christopherson
2022-03-28 18:00 ` Quentin Perret
2022-03-28 18:58 ` Sean Christopherson
2022-03-29 17:01 ` Quentin Perret
2022-03-30 8:58 ` Steven Price
2022-03-30 10:39 ` Quentin Perret
2022-03-30 17:58 ` Sean Christopherson
2022-03-31 16:04 ` Andy Lutomirski
2022-04-01 14:59 ` Quentin Perret
2022-04-01 17:14 ` Sean Christopherson
2022-04-01 18:03 ` Quentin Perret
2022-04-01 18:24 ` Sean Christopherson
2022-04-01 19:56 ` Andy Lutomirski
2022-04-04 15:01 ` Quentin Perret
2022-04-04 17:06 ` Sean Christopherson
2022-04-04 22:04 ` Andy Lutomirski
2022-04-05 10:36 ` Quentin Perret
2022-04-05 17:51 ` Andy Lutomirski
2022-04-05 18:30 ` Sean Christopherson
2022-04-06 18:42 ` Andy Lutomirski
2022-04-06 13:05 ` Quentin Perret
2022-04-05 18:03 ` Sean Christopherson
2022-04-06 10:34 ` Quentin Perret
2022-04-22 10:56 ` Chao Peng
2022-04-22 11:06 ` Paolo Bonzini
2022-04-24 8:07 ` Chao Peng
2022-04-24 16:59 ` Andy Lutomirski
2022-04-25 13:40 ` Chao Peng
2022-04-25 14:52 ` Andy Lutomirski
2022-04-25 20:30 ` Sean Christopherson
2022-06-10 19:18 ` Andy Lutomirski
2022-06-10 19:27 ` Sean Christopherson
2022-04-28 12:29 ` Chao Peng
2022-05-03 11:12 ` Quentin Perret
2022-05-09 22:30 ` Michael Roth
2022-05-09 23:29 ` Sean Christopherson
2022-07-21 20:05 ` Gupta, Pankaj
2022-07-21 21:19 ` Sean Christopherson
2022-07-21 21:36 ` Gupta, Pankaj
2022-07-23 3:09 ` Andy Lutomirski
2022-07-25 9:19 ` Gupta, Pankaj
2022-03-30 16:18 ` Sean Christopherson
2022-03-28 20:16 ` Andy Lutomirski
2022-03-28 22:48 ` Nakajima, Jun
2022-03-29 0:04 ` Sean Christopherson
2022-04-08 21:35 ` Vishal Annapurve
2022-04-12 13:00 ` Chao Peng
2022-04-12 19:58 ` Kirill A. Shutemov
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