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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id g10sm3326023pfh.120.2021.08.26.08.31.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Aug 2021 08:31:10 -0700 (PDT) Date: Thu, 26 Aug 2021 15:31:07 +0000 From: Sean Christopherson To: Vitaly Kuznetsov Cc: kvm@vger.kernel.org, Paolo Bonzini , Wanpeng Li , Jim Mattson , "Dr. David Alan Gilbert" , Nitesh Narayan Lal , Lai Jiangshan , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 4/4] KVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect() Message-ID: References: <20210826122442.966977-1-vkuznets@redhat.com> <20210826122442.966977-5-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210826122442.966977-5-vkuznets@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 26, 2021, Vitaly Kuznetsov wrote: > KASAN reports the following issue: > > BUG: KASAN: stack-out-of-bounds in kvm_make_vcpus_request_mask+0x174/0x440 [kvm] > Read of size 8 at addr ffffc9001364f638 by task qemu-kvm/4798 > > CPU: 0 PID: 4798 Comm: qemu-kvm Tainted: G X --------- --- > Hardware name: AMD Corporation DAYTONA_X/DAYTONA_X, BIOS RYM0081C 07/13/2020 > Call Trace: > dump_stack+0xa5/0xe6 > print_address_description.constprop.0+0x18/0x130 > ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm] > __kasan_report.cold+0x7f/0x114 > ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm] > kasan_report+0x38/0x50 > kasan_check_range+0xf5/0x1d0 > kvm_make_vcpus_request_mask+0x174/0x440 [kvm] > kvm_make_scan_ioapic_request_mask+0x84/0xc0 [kvm] > ? kvm_arch_exit+0x110/0x110 [kvm] > ? sched_clock+0x5/0x10 > ioapic_write_indirect+0x59f/0x9e0 [kvm] > ? static_obj+0xc0/0xc0 > ? __lock_acquired+0x1d2/0x8c0 > ? kvm_ioapic_eoi_inject_work+0x120/0x120 [kvm] > > The problem appears to be that 'vcpu_bitmap' is allocated as a single long > on stack and it should really be KVM_MAX_VCPUS long. We also seem to clear > the lower 16 bits of it with bitmap_zero() for no particular reason (my > guess would be that 'bitmap' and 'vcpu_bitmap' variables in > kvm_bitmap_or_dest_vcpus() caused the confusion: while the later is indeed > 16-bit long, the later should accommodate all possible vCPUs). > > Fixes: 7ee30bc132c6 ("KVM: x86: deliver KVM IOAPIC scan request to target vCPUs") > Fixes: 9a2ae9f6b6bb ("KVM: x86: Zero the IOAPIC scan request dest vCPUs bitmap") > Reported-by: Dr. David Alan Gilbert > Signed-off-by: Vitaly Kuznetsov > Reviewed-by: Maxim Levitsky > --- Reviewed-by: Sean Christopherson