From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qt1-f169.google.com (mail-qt1-f169.google.com [209.85.160.169]) (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 34A08365A13 for ; Fri, 3 Apr 2026 10:01:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775210499; cv=none; b=hNHmuZUyct/vlVdUytr5uDvcpGxp4JhVTAiItOWGqlp3cAJvYWwQH2YEvlACHx+kBBCsXG+6eeZgtMPxM1R6WCn9vpJQqgAsZS8fWAucMy1UlWTYRtyAM61gg1lDCo85TfrL6mxys+csIYdW/JnC/2S51oiWHbZK0C+yph3cObw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775210499; c=relaxed/simple; bh=udt8odhjX6TBaalkLtBPvxUn7Sj70KctvZIGZq8z188=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TXLnv+sNek5j05s2IyNGpwL+l0h+pmnsAPO5Z6uXvknKaTg611PhjiRcL5Dz04exrRBW+uKGxOMZcvxJg5LTD+jW014i4UNA78C+D2jqxfLX8iGY4+xuVbi+i/QZoNzPPjIIxVJeVRVJcNvKjTqx4B7MMYWNaSTpC/G0w25m/1s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=sZdMVYxo; arc=none smtp.client-ip=209.85.160.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="sZdMVYxo" Received: by mail-qt1-f169.google.com with SMTP id d75a77b69052e-5091d71aa11so22353881cf.1 for ; Fri, 03 Apr 2026 03:01:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1775210492; x=1775815292; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=puoXS1QB+flhx5qquPUku4RQL097ct8QKVc2HkG8hr0=; b=sZdMVYxoVb5sl41dIr/Vgq2tQqM1aL4O48l2q89EltbifggbySVdoZoJkfjtDMeRIA 4HsnKyYHmTTttRTBquvPvWH8HJHvAoBUWpDoG2mjvaH9U47dxt6RuEvdPznv156ei7Np CTE7jgTb+9Jtft8RYxBHWSm8qxpGfEj39JCtjGmMcRKHjnx2tsqCzWV85nVmsZqdl0G+ y++finls02Bvk5cF+bhmBtlf1X1TqJGuBI9Ci/cagxmOr3mIUdJGiMNwOY8mKZpQG+Oa wnHmMA3p6kJpSYlRw9wA5JQ3U2Al4bbeTutMsWOW/lyQP4dM7sicMw/xhDzR6pbMYww6 /elg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775210492; x=1775815292; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=puoXS1QB+flhx5qquPUku4RQL097ct8QKVc2HkG8hr0=; b=E0V/qqSVi96MSviOoncyPIazyfGk/5zPi5M+0GGa2l3ry3YhorT6yxWJWwKr043++h dA3s3y+f05T3pz6+x1jX1n1K2hRIH1zcqottVtvGtOzNqvjEbRtmwIH1n46VUoRF6W6L DID749McbhXw2vgUjm2zvpmh243bLwTErzZFoXKiuUBJ6MU3gellwG13H0+xTU/WZCZs f/sfxHMPIApFnLxpHcPksvK0QFMp7GD7O+DNUheOQyCuS4NuC5xXyed9XR+papVJtL/J iJN3To7Fdn2pw2dCYON8/O0SBgY7Stc+Ldhohtn3BPBZ+V/dkaqBjmap+VOMuDTsdYPk efpQ== X-Forwarded-Encrypted: i=1; AJvYcCURDZfWSLIVlIGMCCbnFZ8OlbBbXKj8w+0b1qIz8xm2mz+zsCGO6W8iMB/eiIDd3+A0xv9w5AmQhcmeyzQ=@vger.kernel.org X-Gm-Message-State: AOJu0YxhhD2jerMF5s9vPuQ7LzH3GFlYWYsYUfJCNstYUy1vDQto6yRy uOZdlvTagDk+5L27emu8BU/Lkd2GUz5iF6Fdp7JeKVN689MET26WeNh+ X-Gm-Gg: ATEYQzxvUU5rmnMi26ymlHecgE6trBhgx5YwQVx9dD0CIVBieTdtQA7VW9pXQDkGCyH OyLRwiC3ISJMSlsAbMyVz2bfLcCajtwPnMg3RgG4yrQM+SG6xNMN6PVYjdnT4aNmD5JSRKK9dHv JMcKxDDtZQ1cGBfZrNQwtCLl42qaP9a8hq+6TEkLLrLi296nC8wnCj1pZjFi63ti+SUol6E5/G/ jpAf9DxYLcqzLBxPdzZWlZvNVxAWuoYAtw27aeDOxTzTfwBSiphBxvVc9VFw8dXMro+W3XYIKmr zu57dIKj3q+eWWsVcHz101OZbDdU7h9MqqWfiOhx+9K0oPA1UiVuDvDsZduRyU7ITq7UBOZvny/ ULXsqZ469EsPntFwYBirubVCjnbblYqTlAzHRbuC/Sl1i1icMy12pw7UZWEhfAkCpcY0/+hjnoO CSlV4shAHUZosXKvfwi2eQ6TOyJinIKQ== X-Received: by 2002:ac8:7c55:0:b0:50b:3249:828f with SMTP id d75a77b69052e-50d632c8a04mr26848601cf.28.1775210480761; Fri, 03 Apr 2026 03:01:20 -0700 (PDT) Received: from gmail.com ([20.109.36.234]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50d4b1a3fc7sm53639241cf.5.2026.04.03.03.01.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Apr 2026 03:01:20 -0700 (PDT) From: Ethan Yang To: kvm@vger.kernel.org Cc: xiaoyao.li@intel.com, seanjc@google.com, pbonzini@redhat.com, syzbot+bc0e18379a290e5edfe4@syzkaller.appspotmail.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, x86@kernel.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, glider@google.com Subject: [PATCH v2] KVM: x86: Don't leave APF half-enabled on bad APF data GPA Date: Fri, 3 Apr 2026 10:01:19 +0000 Message-ID: <20260403100119.3311-1-ethan.yang.kernel@gmail.com> X-Mailer: git-send-email @GIT_VERSION@ In-Reply-To: <20260403031111.3171-1-ethan.yang.kernel@gmail.com> References: <20260403031111.3171-1-ethan.yang.kernel@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit kvm_pv_enable_async_pf() updates vcpu->arch.apf.msr_en_val before initializing the APF data gfn_to_hva cache. If userspace provides an invalid GPA, kvm_gfn_to_hva_cache_init() fails, but msr_en_val stays enabled and leaves APF state half-initialized. Later APF paths can then try to use the empty cache and trigger WARN_ON() in kvm_read_guest_offset_cached(). Determine the new APF enabled state from the incoming MSR value, do cache initialization first on the enable path, and commit msr_en_val only after successful initialization. Keep the disable path behavior unchanged. Reported-by: syzbot+bc0e18379a290e5edfe4@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=bc0e18379a290e5edfe4 Link: https://lore.kernel.org/r/aHfD3MczrDpzDX9O@google.com Suggested-by: Sean Christopherson Reviewed-by: Xiaoyao Li Signed-off-by: Ethan Yang --- v2: - Rename helper to __kvm_pv_async_pf_enabled() - Rename new_enabled to enable - Align wrapped line in kvm_gfn_to_hva_cache_init() call --- arch/x86/kvm/x86.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 63afdb6bb07..93b7ad9b52b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1035,11 +1035,16 @@ bool kvm_require_dr(struct kvm_vcpu *vcpu, int dr) } EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_require_dr); -static bool kvm_pv_async_pf_enabled(struct kvm_vcpu *vcpu) +static bool __kvm_pv_async_pf_enabled(u64 data) { u64 mask = KVM_ASYNC_PF_ENABLED | KVM_ASYNC_PF_DELIVERY_AS_INT; - return (vcpu->arch.apf.msr_en_val & mask) == mask; + return (data & mask) == mask; +} + +static bool kvm_pv_async_pf_enabled(struct kvm_vcpu *vcpu) +{ + return __kvm_pv_async_pf_enabled(vcpu->arch.apf.msr_en_val); } static inline u64 pdptr_rsvd_bits(struct kvm_vcpu *vcpu) @@ -3616,6 +3621,7 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info) static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data) { gpa_t gpa = data & ~0x3f; + bool enable; /* Bits 4:5 are reserved, Should be zero */ if (data & 0x30) @@ -3632,18 +3638,20 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data) if (!lapic_in_kernel(vcpu)) return data ? 1 : 0; + enable = __kvm_pv_async_pf_enabled(data); + + if (enable && + kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa, + sizeof(u64))) + return 1; vcpu->arch.apf.msr_en_val = data; - if (!kvm_pv_async_pf_enabled(vcpu)) { + if (!enable) { kvm_clear_async_pf_completion_queue(vcpu); kvm_async_pf_hash_reset(vcpu); return 0; } - if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa, - sizeof(u64))) - return 1; - vcpu->arch.apf.send_always = (data & KVM_ASYNC_PF_SEND_ALWAYS); vcpu->arch.apf.delivery_as_pf_vmexit = data & KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT; -- 2.47.3