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([119.161.98.68]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2985c2bf0f8sm33985925ad.89.2025.11.13.12.09.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Nov 2025 12:09:49 -0800 (PST) From: Nirbhay Sharma To: Jason Gunthorpe , Kevin Tian , Shuah Khan Cc: iommu@lists.linux.dev, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, david.hunter.linux@gmail.com, linux-kernel-mentees@lists.linuxfoundation.org, Nirbhay Sharma Subject: [PATCH] selftests/iommu: Fix array-bounds warning in get_hw_info Date: Fri, 14 Nov 2025 01:38:55 +0530 Message-ID: <20251113200854.429515-2-nirbhay.lkd@gmail.com> X-Mailer: git-send-email 2.48.1 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" GCC warns about potential out-of-bounds access when the test provides a buffer smaller than struct iommu_test_hw_info: iommufd_utils.h:817:37: warning: array subscript 'struct iommu_test_hw_info[0]' is partly outside array bounds of 'struct iommu_test_hw_info_buffer_smaller[1]' [-Warray-bounds=3D] 817 | assert(!info->flags); | ~~~~^~~~~~~ The warning occurs because 'info' is cast to a pointer to the full 8-byte struct at the top of the function, but the buffer_smaller test case passes only a 4-byte buffer. While the code correctly checks data_len before accessing each field, GCC's flow analysis with inlining doesn't recognize that the size check protects the access. Fix this by accessing fields through appropriately-typed pointers that match the actual field sizes (__u32), declared only after the bounds check. This makes the relationship between the size check and memory access explicit to the compiler. Signed-off-by: Nirbhay Sharma --- tools/testing/selftests/iommu/iommufd_utils.h | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/tools/testing/selftests/iommu/iommufd_utils.h b/tools/testing/= selftests/iommu/iommufd_utils.h index 9f472c20c190..37c1b994008c 100644 --- a/tools/testing/selftests/iommu/iommufd_utils.h +++ b/tools/testing/selftests/iommu/iommufd_utils.h @@ -770,7 +770,6 @@ static int _test_cmd_get_hw_info(int fd, __u32 device_i= d, __u32 data_type, void *data, size_t data_len, uint32_t *capabilities, uint8_t *max_pasid) { - struct iommu_test_hw_info *info =3D (struct iommu_test_hw_info *)data; struct iommu_hw_info cmd =3D { .size =3D sizeof(cmd), .dev_id =3D device_id, @@ -810,11 +809,19 @@ static int _test_cmd_get_hw_info(int fd, __u32 device= _id, __u32 data_type, } } =20 - if (info) { - if (data_len >=3D offsetofend(struct iommu_test_hw_info, test_reg)) - assert(info->test_reg =3D=3D IOMMU_HW_INFO_SELFTEST_REGVAL); - if (data_len >=3D offsetofend(struct iommu_test_hw_info, flags)) - assert(!info->flags); + if (data) { + if (data_len >=3D offsetofend(struct iommu_test_hw_info, + test_reg)) { + __u32 *test_reg =3D (__u32 *)data + 1; + + assert(*test_reg =3D=3D IOMMU_HW_INFO_SELFTEST_REGVAL); + } + if (data_len >=3D offsetofend(struct iommu_test_hw_info, + flags)) { + __u32 *flags =3D data; + + assert(!*flags); + } } =20 if (max_pasid) --=20 2.48.1