From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 0A32D175A6B; Sat, 30 May 2026 18:13:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780164840; cv=none; b=eh1PNtraiXdAPbkjrq1fAK6hc9/kErSz+Mn+ivcalJTlt0I8BPv+oBiy4rt9A9L361Vct9IokISyaEQ9zhxiHsRU3JV3Yb+4h7KVC69Ip8vUFJ4YYskI5P1CTw42aHUJDO3EC3xRUoD6nze+HP5+UzEIrkRNK9kZVOscVtYVgV0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780164840; c=relaxed/simple; bh=llQGFZ8m7hQCYaJZHjoF+brNjeXoOvFzjg7UlYJ6Hzc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u5ox0OoxtU/4owQR2pLBERBGHaIVFIJZPFMUXTLJFq/s3oDxyrPDRp2Uy6KrmkjMjEt5k50dIo0I2k1PGNAIEPpkV20K6eveyKU3b7SuokUBikPYK2lSxoDPct0N6F7EN4H1nMnjU6XeZP+dcQqPKbvHypifn5BpKFhMCt3hpL0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XRR/2T9t; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="XRR/2T9t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53F701F00893; Sat, 30 May 2026 18:13:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780164838; bh=KyAwBUUklYopZTOp6GdBw6rbzoi77B248/0COAReGSc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XRR/2T9tzXy+VXG3qW3To5visWDyG/kUbAOfCDtOSgvQ/Z0bWUzz8CDBH4mnw0C16 ZvPEyT5yDTgUaAmX2cz/wfNIjXVENQkoYbQFpgiO+hIQb0IMwhDnCyRxx9ovOqIW9t amaZ7XM9txHgsgxxplv1bT00/g8DoJ1WqKLkipsI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sean Christopherson , Paolo Bonzini , Rajani Kantha <681739313@139.com>, Sasha Levin Subject: [PATCH 5.15 674/776] KVM: x86: Acquire SRCU in KVM_GET_MP_STATE to protect guest memory accesses Date: Sat, 30 May 2026 18:06:28 +0200 Message-ID: <20260530160257.286652982@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160240.228940103@linuxfoundation.org> References: <20260530160240.228940103@linuxfoundation.org> User-Agent: quilt/0.69 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 5.15-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 [ Based on kernel 5.15 available functions, using srcu_read_lock/srcu_read_unlock instead of kvm_vcpu_srcu_read_lock/kvm_vcpu_srcu_read_unlock ] Signed-off-by: Rajani Kantha <681739313@139.com> Signed-off-by: Sasha Levin --- arch/x86/kvm/x86.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a22cd6c0eb0d4..bbfc8ccf4fcd9 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10617,6 +10617,8 @@ int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu, if (kvm_mpx_supported()) kvm_load_guest_fpu(vcpu); + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); + r = kvm_apic_accept_events(vcpu); if (r < 0) goto out; @@ -10630,6 +10632,8 @@ int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu, mp_state->mp_state = vcpu->arch.mp_state; out: + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); + if (kvm_mpx_supported()) kvm_put_guest_fpu(vcpu); vcpu_put(vcpu); -- 2.53.0