KVM Archive on lore.kernel.org
 help / color / Atom feed
From: Sean Christopherson <sean.j.christopherson@intel.com>
To: James Hogan <jhogan@kernel.org>,
	Paul Mackerras <paulus@ozlabs.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Janosch Frank <frankja@linux.ibm.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Marc Zyngier <maz@kernel.org>
Cc: "David Hildenbrand" <david@redhat.com>,
	"Cornelia Huck" <cohuck@redhat.com>,
	"Vitaly Kuznetsov" <vkuznets@redhat.com>,
	"Wanpeng Li" <wanpengli@tencent.com>,
	"Jim Mattson" <jmattson@google.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"James Morse" <james.morse@arm.com>,
	"Julien Thierry" <julien.thierry.kdev@gmail.com>,
	"Suzuki K Poulose" <suzuki.poulose@arm.com>,
	linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org,
	kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
	"Christoffer Dall" <christoffer.dall@arm.com>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>
Subject: Re: [PATCH v4 01/19] KVM: x86: Allocate new rmap and large page tracking when moving memslot
Date: Tue, 17 Dec 2019 12:48:22 -0800
Message-ID: <20191217204822.GC8052@linux.intel.com> (raw)
In-Reply-To: <20191217204041.10815-2-sean.j.christopherson@intel.com>

Dropping non-x86 folks...

This should be included in 5.5 if possible even though the bug has existed
for over a decade.  It's trivially easy for a malicious userspace to
crash KVM and hang the host.  Depending how userspace VMM behavior, it may
even be possible to trigger from a guest.

On Tue, Dec 17, 2019 at 12:40:23PM -0800, Sean Christopherson wrote:
> Reallocate a rmap array and recalcuate large page compatibility when
> moving an existing memslot to correctly handle the alignment properties
> of the new memslot.  The number of rmap entries required at each level
> is dependent on the alignment of the memslot's base gfn with respect to
> that level, e.g. moving a large-page aligned memslot so that it becomes
> unaligned will increase the number of rmap entries needed at the now
> unaligned level.
> 
> Not updating the rmap array is the most obvious bug, as KVM accesses
> garbage data beyond the end of the rmap.  KVM interprets the bad data as
> pointers, leading to non-canonical #GPs, unexpected #PFs, etc...
> 
>   general protection fault: 0000 [#1] SMP
>   CPU: 0 PID: 1909 Comm: move_memory_reg Not tainted 5.4.0-rc7+ #139
>   Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
>   RIP: 0010:rmap_get_first+0x37/0x50 [kvm]
>   Code: <48> 8b 3b 48 85 ff 74 ec e8 6c f4 ff ff 85 c0 74 e3 48 89 d8 5b c3
>   RSP: 0018:ffffc9000021bbc8 EFLAGS: 00010246
>   RAX: ffff00617461642e RBX: ffff00617461642e RCX: 0000000000000012
>   RDX: ffff88827400f568 RSI: ffffc9000021bbe0 RDI: ffff88827400f570
>   RBP: 0010000000000000 R08: ffffc9000021bd00 R09: ffffc9000021bda8
>   R10: ffffc9000021bc48 R11: 0000000000000000 R12: 0030000000000000
>   R13: 0000000000000000 R14: ffff88827427d700 R15: ffffc9000021bce8
>   FS:  00007f7eda014700(0000) GS:ffff888277a00000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 00007f7ed9216ff8 CR3: 0000000274391003 CR4: 0000000000162eb0
>   Call Trace:
>    kvm_mmu_slot_set_dirty+0xa1/0x150 [kvm]
>    __kvm_set_memory_region.part.64+0x559/0x960 [kvm]
>    kvm_set_memory_region+0x45/0x60 [kvm]
>    kvm_vm_ioctl+0x30f/0x920 [kvm]
>    do_vfs_ioctl+0xa1/0x620
>    ksys_ioctl+0x66/0x70
>    __x64_sys_ioctl+0x16/0x20
>    do_syscall_64+0x4c/0x170
>    entry_SYSCALL_64_after_hwframe+0x44/0xa9
>   RIP: 0033:0x7f7ed9911f47
>   Code: <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 21 6f 2c 00 f7 d8 64 89 01 48
>   RSP: 002b:00007ffc00937498 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>   RAX: ffffffffffffffda RBX: 0000000001ab0010 RCX: 00007f7ed9911f47
>   RDX: 0000000001ab1350 RSI: 000000004020ae46 RDI: 0000000000000004
>   RBP: 000000000000000a R08: 0000000000000000 R09: 00007f7ed9214700
>   R10: 00007f7ed92149d0 R11: 0000000000000246 R12: 00000000bffff000
>   R13: 0000000000000003 R14: 00007f7ed9215000 R15: 0000000000000000
>   Modules linked in: kvm_intel kvm irqbypass
>   ---[ end trace 0c5f570b3358ca89 ]---
> 
> The disallow_lpage tracking is more subtle.  Failure to update results
> in KVM creating large pages when it shouldn't, either due to stale data
> or again due to indexing beyond the end of the metadata arrays, which
> can lead to memory corruption and/or leaking data to guest/userspace.
> 
> Note, the arrays for the old memslot are freed by the unconditional call
> to kvm_free_memslot() in __kvm_set_memory_region().
> 
> Fixes: 05da45583de9b ("KVM: MMU: large page support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>  arch/x86/kvm/x86.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8bb2fb1705ff..04d1bf89da0e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9703,6 +9703,13 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
>  {
>  	int i;
>  
> +	/*
> +	 * Clear out the previous array pointers for the KVM_MR_MOVE case.  The
> +	 * old arrays will be freed by __kvm_set_memory_region() if installing
> +	 * the new memslot is successful.
> +	 */
> +	memset(&slot->arch, 0, sizeof(slot->arch));
> +
>  	for (i = 0; i < KVM_NR_PAGE_SIZES; ++i) {
>  		struct kvm_lpage_info *linfo;
>  		unsigned long ugfn;
> @@ -9777,6 +9784,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  				const struct kvm_userspace_memory_region *mem,
>  				enum kvm_mr_change change)
>  {
> +	if (change == KVM_MR_MOVE)
> +		return kvm_arch_create_memslot(kvm, memslot,
> +					       mem->memory_size >> PAGE_SHIFT);
> +
>  	return 0;
>  }
>  
> -- 
> 2.24.1
> 

  reply index

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 20:40 [PATCH v4 00/19] KVM: Dynamically size memslot arrays Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 01/19] KVM: x86: Allocate new rmap and large page tracking when moving memslot Sean Christopherson
2019-12-17 20:48   ` Sean Christopherson [this message]
2019-12-17 20:50     ` Sean Christopherson
2019-12-17 21:56   ` Peter Xu
2019-12-17 22:20     ` Sean Christopherson
2019-12-17 22:37       ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 02/19] KVM: Reinstall old memslots if arch preparation fails Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 03/19] KVM: Don't free new memslot if allocation of said memslot fails Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 04/19] KVM: PPC: Move memslot memory allocation into prepare_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 05/19] KVM: x86: Allocate memslot resources during prepare_memory_region() Sean Christopherson
2019-12-17 22:07   ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 06/19] KVM: Drop kvm_arch_create_memslot() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 07/19] KVM: Explicitly free allocated-but-unused dirty bitmap Sean Christopherson
2019-12-17 22:24   ` Peter Xu
2019-12-17 22:51     ` Sean Christopherson
2019-12-18 16:17       ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 08/19] KVM: Refactor error handling for setting memory region Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 09/19] KVM: Move setting of memslot into helper routine Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 10/19] KVM: Drop "const" attribute from old memslot in commit_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 11/19] KVM: x86: Free arrays for old memslot when moving memslot's base gfn Sean Christopherson
2019-12-17 22:48   ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 12/19] KVM: Move memslot deletion to helper function Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 13/19] KVM: Simplify kvm_free_memslot() and all its descendents Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 14/19] KVM: Clean up local variable usage in __kvm_set_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 15/19] KVM: Provide common implementation for generic dirty log functions Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 16/19] KVM: Ensure validity of memslot with respect to kvm_get_dirty_log() Sean Christopherson
2019-12-24 18:19   ` Peter Xu
2020-01-14 18:25     ` Sean Christopherson
2020-02-06 22:03       ` Peter Xu
2020-02-07 18:52         ` Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 17/19] KVM: Terminate memslot walks via used_slots Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 18/19] KVM: Dynamically size memslot array based on number of used slots Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 19/19] KVM: selftests: Add test for KVM_SET_USER_MEMORY_REGION Sean Christopherson
2019-12-18 11:29   ` Christian Borntraeger
2019-12-18 11:39   ` Christian Borntraeger
2019-12-18 16:39     ` Sean Christopherson
2020-03-24  9:43       ` Christian Borntraeger
2020-03-24 18:20         ` Sean Christopherson
2019-12-18 11:40 ` [PATCH v4 00/19] KVM: Dynamically size memslot arrays Christian Borntraeger
2019-12-18 18:10 ` Marc Zyngier

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191217204822.GC8052@linux.intel.com \
    --to=sean.j.christopherson@intel.com \
    --cc=borntraeger@de.ibm.com \
    --cc=christoffer.dall@arm.com \
    --cc=cohuck@redhat.com \
    --cc=david@redhat.com \
    --cc=f4bug@amsat.org \
    --cc=frankja@linux.ibm.com \
    --cc=james.morse@arm.com \
    --cc=jhogan@kernel.org \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=julien.thierry.kdev@gmail.com \
    --cc=kvm-ppc@vger.kernel.org \
    --cc=kvm@vger.kernel.org \
    --cc=kvmarm@lists.cs.columbia.edu \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mips@vger.kernel.org \
    --cc=maz@kernel.org \
    --cc=paulus@ozlabs.org \
    --cc=pbonzini@redhat.com \
    --cc=suzuki.poulose@arm.com \
    --cc=vkuznets@redhat.com \
    --cc=wanpengli@tencent.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git