From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 08EB214EC47 for ; Wed, 7 Aug 2024 21:58:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723067919; cv=none; b=ibVDIH6siW2NDDRwYB9RFoFtgpQ9JIblxWkUxq/fWvlUYLbY3xJUy7+kEcYiPVUDH3zVX1hxvk8JXjFmZvmN3kBNtZvS/smlLKSYSd/GkSbqVqDO2pnnYM6tsUX8RwbqUHzfnLTXH8BIvB3s0EwGqcjYS7TWFzVmoGDNCAwW044= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723067919; c=relaxed/simple; bh=c08WaZBC8OmswkebMYegQBqCu6JB2zC4KsS+DBX2LfE=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=EMQggiramdnS9ALxm6Ii22Rwo/bg6e/fJcwNFqVeGJdc9zRWP98MFrZgtmq/dJ4D5buiQRdj0tIiNe5N5KxGVe7WVR+0TBu5+FeVaJ/H6eaQE0kuHqTig4etycvT4NN2QZKhKQ28uaUekJC48c4Nul1jWDH5weOEYhHUrkj8uts= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=1h9QXAV1; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="1h9QXAV1" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-5e4df21f22dso236442a12.0 for ; Wed, 07 Aug 2024 14:58:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1723067917; x=1723672717; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Geo7mE7Px+nMYERQfpI51YnWlkJ5yKR6d+PPNKtIfZQ=; b=1h9QXAV1Irw1QSzpeqV+TQWks+Rhmd9eCuMy5Gqs+dcyUZ4AdC4qiR5Tz/G+iriDCo 0n5VMiVYP6DcuPSolS5eQwJwrCs6mrA6tgt3DnIYj8IcMqyYSiHhT2ceZ60LQ5seFCFJ 0Qi3868ODZ8oR+IAFMeY1ACsgFydz0B5qXTLkCJZ5YLJzdsBkK8nTJ5kOmB9SeDgdTS7 5MI06yNZ53EO/y8XzBIswEk70DiMw9bq+yovnVf2Ty+X2+C7XcSObZgL/WJ1uLC3LRp5 aw3FgjMm3vE3V7pk6lgek+dfLStFHLnSkWxkifq7iOkCDWGncdBAmIcAvW4ngsSvgMFL qwgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1723067917; x=1723672717; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Geo7mE7Px+nMYERQfpI51YnWlkJ5yKR6d+PPNKtIfZQ=; b=Va3zXeH5MMXCn6kL1veAQQbBun8EJlmdp/hUXgvM2A3FV+j4F92tFKmEmHdgDiEIpJ BHNOM32uzFvZ7O3ep1ylG+FD93RBdnWBH5hoXHwamcbnLmpGRB4zSma4CMREeXsCQLW0 cPAIdE0ZMUT9pSe7qFhlb9yqGUwKxuwjvsYfdjNqnzElxyaUd9pXwfI6cgKorKwJpkfD liViMzvv1soIGRZxsRYdnhDkSjZriACO2cfhpHvnlLdaTBt2RRpDsn4Z7ahxNhdb2dv2 UTP2kf8hP8BgtdHBTRB+DJ27vKXUsmMDjWb0t9fPttclGkWcABCl1M1oYggYid8kwC8R dQEg== X-Forwarded-Encrypted: i=1; AJvYcCWKhSG3+aJo+nsiMhyZxc0aE8C09/wrkLUtgePVjw+QDeKLHp33KZYB81xyLZlJCRdPTVY=@vger.kernel.org X-Gm-Message-State: AOJu0Yz4qIGgOhtPpIknpu/kGiHuiVmQKqFnIDLoJykFLBFBbqSJkRTI hEyn8VW+O1h/UOCQ1gPmnIE2Ily135ACEECyvCV6eMjr97bh10ZXQI79hiDdsMh0/7PGBeXNoCJ hJg== X-Google-Smtp-Source: AGHT+IGT4yfaQtCszwo3v/BQf+VsEDoi91mBnnPGweFALLFNPlxrCzIoFqDGdSNEdxfNC5erws8GJco3fog= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a63:935a:0:b0:702:4fb6:8724 with SMTP id 41be03b00d2f7-7c11124f056mr7890a12.1.1723067917038; Wed, 07 Aug 2024 14:58:37 -0700 (PDT) Date: Wed, 7 Aug 2024 14:58:35 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240730155646.1687-1-will@kernel.org> <20240731133118.GA2946@willie-the-truck> <3e5f7422-43ce-44d4-bff7-cc02165f08c0@rbox.co> <20240801124131.GA4730@willie-the-truck> <07987fc3-5c47-4e77-956c-dae4bdf4bc2b@rbox.co> Message-ID: Subject: Re: [PATCH] KVM: Fix error path in kvm_vm_ioctl_create_vcpu() on xa_store() failure From: Sean Christopherson To: Michal Luczaj Cc: Will Deacon , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Paolo Bonzini , Alexander Potapenko , Marc Zyngier Content-Type: text/plain; charset="us-ascii" On Tue, Aug 06, 2024, Michal Luczaj wrote: > On 8/6/24 00:56, Sean Christopherson wrote: > > [...] > > + /* > > + * xa_store() should never fail, see xa_reserve() above. Leak the vCPU > > + * if the impossible happens, as userspace already has access to the > > + * vCPU, i.e. freeing the vCPU before userspace puts its file reference > > + * would trigger a use-after-free. > > + */ > > if (KVM_BUG_ON(xa_store(&kvm->vcpu_array, vcpu->vcpu_idx, vcpu, 0), kvm)) { > > - r = -EINVAL; > > - goto kvm_put_xa_release; > > + mutex_unlock(&vcpu->mutex); > > + return -EINVAL; > > } > > > > /* > > @@ -4302,6 +4310,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, unsigned long id) > > */ > > smp_wmb(); > > atomic_inc(&kvm->online_vcpus); > > + mutex_unlock(&vcpu->mutex); > > > > mutex_unlock(&kvm->lock); > > kvm_arch_vcpu_postcreate(vcpu); > > @@ -4309,6 +4318,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, unsigned long id) > > return r; > > > > kvm_put_xa_release: > > + mutex_unlock(&vcpu->mutex); > > kvm_put_kvm_no_destroy(kvm); > > xa_release(&kvm->vcpu_array, vcpu->vcpu_idx); > > Since we're handling the impossible, isn't the BUG_ON part missing > mutex_unlock(&kvm->lock)? Doh, yes.