From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A894D256C6D; Thu, 17 Apr 2025 18:13:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744913636; cv=none; b=hrxtQnAvsfOFP2Ab8h1HWrdyPZ/CCxM1QEtpqhxp5gqnLlLtHBNxVLRWjIdF1x/o464Wc3WuIuL/AQfbtIShAKVo5eUOJJGmCdIWObLDP2JI2kNyFAUPOSMwcPqxm17tVOhZnxEYmWE1T+l3jrdguqz+96Q8RLWhp+43EeErTRs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744913636; c=relaxed/simple; bh=BFfIWSSJVhBFNRNlbGvBV0Nt6hmlrA6noDpmQ34Yr7s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DbXkE2lNG9tcpSWzWa/TrEJUizhej7l3b6iR/jH+0bnzzTXZbRDR/naHEpb2Y6KthqUPE3iw9bc5pMyZv+Tf1S7wQCnwXBxgBgXfTQmDuWcqVIHnF7bb8cDI4yQ5E6uwLaLrnBvf7BcMoIidrkeZtfrZaSO9FCRvSlnztjXrD/M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ciN65E4x; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ciN65E4x" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30478C4CEE4; Thu, 17 Apr 2025 18:13:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744913636; bh=BFfIWSSJVhBFNRNlbGvBV0Nt6hmlrA6noDpmQ34Yr7s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ciN65E4xoBPGxo4iWAGP1GUiolWP7mtGadEw+ylcbrPOAWvHgM/7AyRgm2vfneAgb FIH4nRl0gciel2x2PpLzunX1jmDjaAcMk4mfIg5os1VcEOFW6cc7zl7giTj2C36NM2 7Pjd6m5/KCW4SotqaWUwNfUoLaA0JFwqdQhf5Rus= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sean Christopherson , Paolo Bonzini Subject: [PATCH 6.14 404/449] KVM: x86: Acquire SRCU in KVM_GET_MP_STATE to protect guest memory accesses Date: Thu, 17 Apr 2025 19:51:32 +0200 Message-ID: <20250417175134.528964318@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250417175117.964400335@linuxfoundation.org> References: <20250417175117.964400335@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sean Christopherson commit ef01cac401f18647d62720cf773d7bb0541827da upstream. Acquire a lock on kvm->srcu when userspace is getting MP state to handle a rather extreme edge case where "accepting" APIC events, i.e. processing pending INIT or SIPI, can trigger accesses to guest memory. If the vCPU is in L2 with INIT *and* a TRIPLE_FAULT request pending, then getting MP state will trigger a nested VM-Exit by way of ->check_nested_events(), and emuating the nested VM-Exit can access guest memory. The splat was originally hit by syzkaller on a Google-internal kernel, and reproduced on an upstream kernel by hacking the triple_fault_event_test selftest to stuff a pending INIT, store an MSR on VM-Exit (to generate a memory access on VMX), and do vcpu_mp_state_get() to trigger the scenario. ============================= WARNING: suspicious RCU usage 6.14.0-rc3-b112d356288b-vmx/pi_lockdep_false_pos-lock #3 Not tainted ----------------------------- include/linux/kvm_host.h:1058 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by triple_fault_ev/1256: #0: ffff88810df5a330 (&vcpu->mutex){+.+.}-{4:4}, at: kvm_vcpu_ioctl+0x8b/0x9a0 [kvm] stack backtrace: CPU: 11 UID: 1000 PID: 1256 Comm: triple_fault_ev Not tainted 6.14.0-rc3-b112d356288b-vmx #3 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: dump_stack_lvl+0x7f/0x90 lockdep_rcu_suspicious+0x144/0x190 kvm_vcpu_gfn_to_memslot+0x156/0x180 [kvm] kvm_vcpu_read_guest+0x3e/0x90 [kvm] read_and_check_msr_entry+0x2e/0x180 [kvm_intel] __nested_vmx_vmexit+0x550/0xde0 [kvm_intel] kvm_check_nested_events+0x1b/0x30 [kvm] kvm_apic_accept_events+0x33/0x100 [kvm] kvm_arch_vcpu_ioctl_get_mpstate+0x30/0x1d0 [kvm] kvm_vcpu_ioctl+0x33e/0x9a0 [kvm] __x64_sys_ioctl+0x8b/0xb0 do_syscall_64+0x6c/0x170 entry_SYSCALL_64_after_hwframe+0x4b/0x53 Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-ID: <20250401150504.829812-1-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11773,6 +11773,8 @@ int kvm_arch_vcpu_ioctl_get_mpstate(stru if (kvm_mpx_supported()) kvm_load_guest_fpu(vcpu); + kvm_vcpu_srcu_read_lock(vcpu); + r = kvm_apic_accept_events(vcpu); if (r < 0) goto out; @@ -11786,6 +11788,8 @@ int kvm_arch_vcpu_ioctl_get_mpstate(stru mp_state->mp_state = vcpu->arch.mp_state; out: + kvm_vcpu_srcu_read_unlock(vcpu); + if (kvm_mpx_supported()) kvm_put_guest_fpu(vcpu); vcpu_put(vcpu);