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Tue, 2 Feb 2021 07:10:26 +0000 Subject: Re: [PATCH bpf v3 1/3] bpf: update local storage test to check handling of null ptrs To: Andrii Nakryiko , KP Singh CC: bpf , Gilad Reti , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau References: <20210112075525.256820-1-kpsingh@kernel.org> <20210112075525.256820-2-kpsingh@kernel.org> From: Yonghong Song Message-ID: Date: Mon, 1 Feb 2021 23:10:21 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Originating-IP: [2620:10d:c090:400::5:c99d] X-ClientProxiedBy: MW4PR03CA0059.namprd03.prod.outlook.com (2603:10b6:303:8e::34) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2620:10d:c085:21c1::11fb] (2620:10d:c090:400::5:c99d) by MW4PR03CA0059.namprd03.prod.outlook.com (2603:10b6:303:8e::34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.18 via Frontend Transport; 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This change incorporates the example suggested in [1] into >>>> the local storage selftest. >>>> >>>> The test is updated to create a temporary directory instead of just >>>> using a tempfile. In order to replicate the issue this copied rm binary >>>> is renamed tiggering the inode_rename with a null pointer for the >>>> new_inode. The logic to verify the setting and deletion of the inode >>>> local storage of the old inode is also moved to this LSM hook. >>>> >>>> The change also removes the copy_rm function and simply shells out >>>> to copy files and recursively delete directories and consolidates the >>>> logic of setting the initial inode storage to the bprm_committed_creds >>>> hook and removes the file_open hook. >>>> >>>> [1]: https://lore.kernel.org/bpf/CANaYP3HWkH91SN=wTNO9FL_2ztHfqcXKX38SSE-JJ2voh+vssw@mail.gmail.com >>>> >>>> Suggested-by: Gilad Reti >>>> Acked-by: Yonghong Song >>>> Signed-off-by: KP Singh >>>> --- >>> >>> Hi KP, >>> >>> I'm getting a compilation warning when building selftests. Can you >>> please take a look and send a fix? Thanks! >>> >>> /data/users/andriin/linux/tools/testing/selftests/bpf/prog_tests/test_local_storage.c: >>> In function ‘test_test_local_storage’: >>> /data/users/andriin/linux/tools/testing/selftests/bpf/prog_tests/test_local_storage.c:143:52: >>> warning: ‘/copy_of_rm’ directive output may be truncated writing 11 >>> bytes into a region of size between 1 and 64 [-Wformat-truncation=] >>> 143 | snprintf(tmp_exec_path, sizeof(tmp_exec_path), "%s/copy_of_rm", >>> | ^~~~~~~~~~~ >>> /data/users/andriin/linux/tools/testing/selftests/bpf/prog_tests/test_local_storage.c:143:2: >>> note: ‘snprintf’ output between 12 and 75 bytes into a destination of >>> size 64 >>> 143 | snprintf(tmp_exec_path, sizeof(tmp_exec_path), "%s/copy_of_rm", >>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> 144 | tmp_dir_path); >>> | ~~~~~~~~~~~~~ >>> >> >> I don't seem to get this warning, so maybe we are using different compilers. >> >> Mine is gcc 10.2.1 20201224 (from debian) > > Funny enough, but I can't repro it locally anymore. I have gcc 10.2.0. > But your suggested fix below does look like a correct one, so feel > free to send it over, thanks! > >> >> That said, I understand why it's complaining, it's for something that >> cannot really happen: >> >> tmp_dir_path cannot be 64 because we actually know its length so the >> tmp_exec_path cannot really overflow 64 bytes. >> >> Can you check if the following patch makes it go away? >> >> diff --git a/tools/testing/selftests/bpf/prog_tests/test_local_storage.c >> b/tools/testing/selftests/bpf/prog_tests/test_local_storage.c >> index 3bfcf00c0a67..d2c16eaae367 100644 >> --- a/tools/testing/selftests/bpf/prog_tests/test_local_storage.c >> +++ b/tools/testing/selftests/bpf/prog_tests/test_local_storage.c >> @@ -113,7 +113,7 @@ static bool check_syscall_operations(int map_fd, int obj_fd) >> >> void test_test_local_storage(void) >> { >> - char tmp_dir_path[64] = "/tmp/local_storageXXXXXX"; >> + char tmp_dir_path[] = "/tmp/local_storageXXXXXX"; >> int err, serv_sk = -1, task_fd = -1, rm_fd = -1; >> struct local_storage *skel = NULL; >> char tmp_exec_path[64]; >> >> If so, I can send you a fix. I have gcc 8.2.1 which can reproduce the issue. With the above fix, the warning is gone. So yes, please send a fix. Thanks! >> >> - KP >> >>> >>>> .../bpf/prog_tests/test_local_storage.c | 96 +++++-------------- >>>> .../selftests/bpf/progs/local_storage.c | 62 ++++++------ >>>> 2 files changed, 61 insertions(+), 97 deletions(-) >>>> >>> >>> [...]