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Mon, 09 Mar 2026 00:57:38 -0700 (PDT) Received: from localhost.localdomain ([147.136.157.3]) by smtp.googlemail.com with ESMTPSA id 98e67ed59e1d1-359c0154a09sm10039968a91.12.2026.03.09.00.57.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Mar 2026 00:57:38 -0700 (PDT) From: phind.uet@gmail.com To: Paolo Bonzini Cc: Nguyen Dinh Phi , syzbot+cde12433b6c56f55d9ed@syzkaller.appspotmail.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] KVM: pfncache: Fix uhva validity check in kvm_gpc_is_valid_len() Date: Mon, 9 Mar 2026 15:56:29 +0800 Message-ID: <20260309075629.24569-2-phind.uet@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Nguyen Dinh Phi In kvm_gpc_is_valid_len(), if the GPA is an error GPA, the function uses uhva to calculate the page offset. However, if uhva is invalid, its value can still be page-aligned (for example, PAGE_OFFSET) and this function will still return true. An invalid uhva could lead to incorrect offset calculations and potentially trigger a WARN_ON_ONCE in __kvm_gpc_refresh(). Fixing it by adding an additional check for uhva. Signed-off-by: Nguyen Dinh Phi Reported-by: syzbot+cde12433b6c56f55d9ed@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Dcde12433b6c56f55d9ed --- virt/kvm/pfncache.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 728d2c1b488a..707ead0a096c 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -60,8 +60,16 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, = unsigned long start, static bool kvm_gpc_is_valid_len(gpa_t gpa, unsigned long uhva, unsigned long len) { - unsigned long offset =3D kvm_is_error_gpa(gpa) ? offset_in_page(uhva) : - offset_in_page(gpa); + unsigned long offset; + + if (kvm_is_error_gpa(gpa)) { + if (kvm_is_error_hva(uhva)) + return false; + + offset =3D offset_in_page(uhva); + } else { + offset =3D offset_in_page(gpa); + } =20 /* * The cached access must fit within a single page. The 'len' argument --=20 2.43.0