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Sat, 5 Dec 2020 19:11:28 +0000 Subject: Re: [PATCH bpf] tools/bpftool: fix PID fetching with a lot of results To: Andrii Nakryiko , , , , CC: References: <20201204232002.3589803-1-andrii@kernel.org> From: Yonghong Song Message-ID: Date: Sat, 5 Dec 2020 11:11:25 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 In-Reply-To: <20201204232002.3589803-1-andrii@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [2620:10d:c090:400::5:d155] X-ClientProxiedBy: CO1PR15CA0088.namprd15.prod.outlook.com (2603:10b6:101:20::32) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2620:10d:c085:21c1::1033] (2620:10d:c090:400::5:d155) by CO1PR15CA0088.namprd15.prod.outlook.com (2603:10b6:101:20::32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3632.17 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?M0ZLUG12L0J0MWFGMk5FTEIyY2haVGxCZFJCakRlMUQvamxBZXVDRVpna1hw?= =?utf-8?B?bmNPdWRVZG5mTmhWamIycmt4bzRZSmZOeDI5eWpwdTgzMDRiaEFaUDA2cVQz?= =?utf-8?B?L2lpclRCY09aYVlYY2FpcHM0YmhKNWpaYkV4Q2JLRWdXZjRtMURRVWNtVy9Q?= =?utf-8?B?d252UGdLNU5uMDM2S3FIM3VpUmUyYWRxa0NRWmNaSnJiQVJtN0NZZkk1bGNQ?= =?utf-8?B?Szk5TXVMREFtZmVjOWhyeEV0azY3U2lhV2tiVlNibHpZMG1ZazBzWm1WOFo5?= =?utf-8?B?MkR4dDNYNHJ2elRKeFE1ajBjRTZFSEtHOUdoR3VGYmY0Ri9Hdkd4bGNkclVX?= =?utf-8?B?N1ZFN3FqVjZaQkxZNGNMdS9ENHdrYk1FWFFRYjFMNFh4b3pkUWJUMnJyb09s?= =?utf-8?B?MFcxczdyS3lYbFdaNnVSNmtGSlBCd1phT2JFVSsxZEY0RWh6UmltZjZBS05B?= =?utf-8?B?ZUlYRHNBN1I1UW5DaWdVL25pMHV5V3l3TG5obFBLK2FheXhiR24waFBrWThj?= =?utf-8?B?SjNSS2IvY0NqeEFkWGYxeStpYjZFMDM3WkJHMityMzRJTVlyNnN4QkNQaDE2?= =?utf-8?B?SXlDTVpwOFh6VGQ5Uy85U1JpOEtMcXJPRWdCMWlnYndHYUxNM0ZZQS9TV2xo?= =?utf-8?B?d21ZeklSeVJSOU5qSllQeWZsZVlqN0NtM0Z4c3pYMmI5aXhIVkdGYzZnQWd3?= =?utf-8?B?NFRTOHE5OVhVWHRrWDEvUlNwenRKMmpwM2tQNHJzZXpyc0dlZHlmVTV3aE0r?= =?utf-8?B?UzlmbjRYcDlzelVyUkNZcHVTTE4xYTRESDZtQTE5VkQzNExHZE82S1NReVY5?= =?utf-8?B?YUV2TEd6WUZ0N0I1VThWMVk3Rkc1d1FVQU9xTUdIeHNTdDNQNmp4RDdrQkRX?= =?utf-8?B?M3BRY1R0K3h3QW1yeGpTYUM0RmZqUk5rMCt3YUhZdXR0aDNSVDRGV0RXOE9p?= =?utf-8?B?TU4wOVJuOWlWb2FTQmp4ZmJDRWZWOU1YUDBBWU9KQlZtYXcxYmp6VmFwQld0?= =?utf-8?B?YWIvTERGaTNwb3FzVFl2ZVlLQmw0blhIcWlPMjE5UWhaeFR6cmU1RTJuZGt2?= =?utf-8?B?WFQ5bHcxaTdKVUVHdVh4UmFLQ2cwMXhPVTJjSjR6bTZJNlRwN3FRL3hDZTk0?= =?utf-8?B?RzMxVW1KMXRnSmJqMmZuR0xMNUtwc01BenhLZ3ZqMEtWSWNqdnJXaG1vUklt?= =?utf-8?B?WkdWOVUzNVQ5VFBtR0hZcGZCTVJ0RUVSbjdhNTdPQlRkN3d2b0NvNFcrbHhn?= =?utf-8?B?MXRWWUw2Qk4rY2V0eHpNNE4xUnhKT2NrekZhWkZCUlMwaEljQXhIQU1VMzlG?= =?utf-8?B?Ris1V1F3eVNkazM4dmZOTzRlQ0FYUUJidWROelppaXpLRVVKalRhQlhBRU14?= =?utf-8?B?NFJ0ZTYrUEJoZUE9PQ==?= X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4088.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Dec 2020 19:11:28.4008 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-Network-Message-Id: a0a47f11-37e6-4fa1-a648-08d89951917f X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: jU+6LtHapugWKGpkjhq0hm/ty82LrOBuudB8w4QnrB55fY4eZq1j3YpUAJv8Wquv X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2328 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-12-05_15:2020-12-04,2020-12-05 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 malwarescore=0 bulkscore=0 adultscore=0 mlxscore=0 suspectscore=0 impostorscore=0 clxscore=1015 lowpriorityscore=0 phishscore=0 mlxlogscore=999 priorityscore=1501 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012050127 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 12/4/20 3:20 PM, Andrii Nakryiko wrote: > In case of having so many PID results that they don't fit into a singe page > (4096) bytes, bpftool will erroneously conclude that it got corrupted data due > to 4096 not being a multiple of struct pid_iter_entry, so the last entry will > be partially truncated. Fix this by sizing the buffer to fit exactly N entries > with no truncation in the middle of record. > > Fixes: d53dee3fe013 ("tools/bpftool: Show info for processes holding BPF map/prog/link/btf FDs") > Signed-off-by: Andrii Nakryiko Ack with one nit below. Acked-by: Yonghong Song > --- > tools/bpf/bpftool/pids.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/bpf/bpftool/pids.c b/tools/bpf/bpftool/pids.c > index df7d8ec76036..477e55d59c34 100644 > --- a/tools/bpf/bpftool/pids.c > +++ b/tools/bpf/bpftool/pids.c > @@ -89,9 +89,9 @@ libbpf_print_none(__maybe_unused enum libbpf_print_level level, > > int build_obj_refs_table(struct obj_refs_table *table, enum bpf_obj_type type) > { > - char buf[4096]; > - struct pid_iter_bpf *skel; > struct pid_iter_entry *e; > + char buf[4096 / sizeof(*e) * sizeof(*e)]; > + struct pid_iter_bpf *skel; No need to move "struct pid_iter_bpf *skel", right? > int err, ret, fd = -1, i; > libbpf_print_fn_t default_print; > >