linux-kernel - Re: [PATCH v6 01/22] KVM: x86: Allocate new rmap and large page tracking when moving memslot

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]

Message-ID: <20200219191017.GA37550@xz-x1>
Date:   Wed, 19 Feb 2020 14:10:17 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        Christoffer Dall <christoffer.dall@....com>,
        Philippe Mathieu-Daudé <f4bug@...at.org>
Subject: Re: [PATCH v6 01/22] KVM: x86: Allocate new rmap and large page
 tracking when moving memslot

On Tue, Feb 18, 2020 at 01:07:15PM -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@...r.kernel.org
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>

Reviewed-by: Peter Xu <peterx@...hat.com>

-- 
Peter Xu