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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id x5-20020a17090aa38500b00219cf5c3829sm1658597pjp.57.2023.01.05.11.05.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Jan 2023 11:05:50 -0800 (PST) From: Kees Cook To: Sean Christopherson Cc: Kees Cook , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "Gustavo A. R. Silva" , x86@kernel.org, "H. Peter Anvin" , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] KVM: x86: Replace 0-length arrays with flexible arrays Date: Thu, 5 Jan 2023 11:05:49 -0800 Message-Id: <20230105190548.never.323-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2361; h=from:subject:message-id; bh=4Cc5ATtGGJ62WdR/RRtEjd3vcbEKzg9EcvjLs50yP4M=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBjtx+Mrzj8257RzFFkg/QcFRjziiNI/h5hA61oodCI Vw30ef6JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCY7cfjAAKCRCJcvTf3G3AJhZJEA CY04hWGr+64pn8pHkpIMM8qmZt2aB4+QuzuYa8dsIb5raXrCgCp1UpUfMiptB8MLEpv1H2YploSa0e H6KMgqEDSkpuqO73fM8QyWWWNxmljXMCXEq+Ya1FWzdHSBTaqI1SHWrrogWGrrjCvkh+vXfnBzbUto +Raa3tL/ME4x20W4QyCxP6bXJ0mby6HKC1l8rSNRJMGjW4nvD82e4E1XquDk6zM6jXfgGC/lDi4B8a 6FNrTOEjG4Lk9UX8UhU5Qayt9SWDoP5YcwUyEQnzxv0N5ACTZmV5fO4PTZFG3t7k6G19aKbknxzDe9 7M8NHS26L+kk5zqfLHhXMpHBzxvsn28PiShxfbBcKSBt4usMLaqLSs2t4LdHYujcFEZMPN2+K7mPjq lOzJCSnCHj2GAf6ZnSldlsXzzCADUi2W0XfgH+obT5xBfpwVRiVYDUFEDhdA3jyNczFc17+oG7Xi+m ZiLH0nSOVB4c0eTX/RNOkdIaZtBZaNHnGtgz6Sa1oDCNQG+txyWgdtbDSAi71EOIdcHgpV5lGNeQgp R/zMzFDNUC9oM4Paci2nfc+5ABN3b9NRLto1HiLQ3X8acOGnQi/NfL2UPWdT3uw48FbvPsgQgyE+p3 3qVYoWllPMvdNy88+wtjoYN+QivCmDaG1y7CfcpApnvI0i1oSP2MZqIXStgg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Zero-length arrays are deprecated[1]. Replace struct kvm_nested_state's "data" union 0-length arrays with flexible arrays. (How are the sizes of these arrays verified?) Detected with GCC 13, using -fstrict-flex-arrays=3D3: arch/x86/kvm/svm/nested.c: In function 'svm_get_nested_state': arch/x86/kvm/svm/nested.c:1536:17: error: array subscript 0 is outside arra= y bounds of 'struct kvm_svm_nested_state_data[0]' [-Werror=3Darray-bounds= =3D] 1536 | &user_kvm_nested_state->data.svm[0]; | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from include/uapi/linux/kvm.h:15, from include/linux/kvm_host.h:40, from arch/x86/kvm/svm/nested.c:18: arch/x86/include/uapi/asm/kvm.h:511:50: note: while referencing 'svm' 511 | struct kvm_svm_nested_state_data svm[0]; | ^~~ [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-len= gth-and-one-element-arrays Cc: Sean Christopherson Cc: Paolo Bonzini Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "Gustavo A. R. Silva" Cc: x86@kernel.org Cc: "H. Peter Anvin" Cc: kvm@vger.kernel.org Signed-off-by: Kees Cook Reviewed-by: Sean Christopherson --- arch/x86/include/uapi/asm/kvm.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kv= m.h index e48deab8901d..8ec3dfd641b0 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -502,13 +502,13 @@ struct kvm_nested_state { } hdr; =20 /* - * Define data region as 0 bytes to preserve backwards-compatability + * Define union of flexible arrays to preserve backwards-compatability * to old definition of kvm_nested_state in order to avoid changing * KVM_{GET,PUT}_NESTED_STATE ioctl values. */ union { - struct kvm_vmx_nested_state_data vmx[0]; - struct kvm_svm_nested_state_data svm[0]; + __DECLARE_FLEX_ARRAY(struct kvm_vmx_nested_state_data, vmx); + __DECLARE_FLEX_ARRAY(struct kvm_svm_nested_state_data, svm); } data; }; =20 --=20 2.34.1