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Mon, 22 Dec 2025 02:57:02 -0800 (PST) X-Google-Smtp-Source: AGHT+IHOZ8Mg+irUUx00i70JUySVxbyZwgHrGLx5tvOrAi1bLKJOKaGccjgn0j03pYHiWhdTj5a1Q62kHvVuiw4oyZ4= X-Received: by 2002:a05:7300:c01b:10b0:2b0:58aa:8852 with SMTP id 5a478bee46e88-2b05ec6d746mr10200088eec.22.1766401021797; Mon, 22 Dec 2025 02:57:01 -0800 (PST) MIME-Version: 1.0 References: <20251221122639.3168038-1-liwang@redhat.com> <20251221122639.3168038-2-liwang@redhat.com> <20251221221052.3b769fc2@pumpkin> <20251222094828.2783d9e5@pumpkin> In-Reply-To: <20251222094828.2783d9e5@pumpkin> From: Li Wang Date: Mon, 22 Dec 2025 18:56:49 +0800 X-Gm-Features: AQt7F2rMyTWRAgL_U5eetjBYd2cn7LdFDTq8E1pI5bUehmtEffvK18MPJsl7YCg Message-ID: Subject: Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as size_t To: David Laight , Andrew Morton Cc: linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand , Mark Brown , Shuah Khan , Waiman Long X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: qwsH0HW8KkjQyMhy9QCUfuH0MzCdXAhtuu2yZBBwA1E_1766401022 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: shsygd39fd3htz8wemtoo5s3j14qh8mp X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: CA45A1C0004 X-HE-Tag: 1766401025-214517 X-HE-Meta: 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 wiQB/68R 8cJ0+GsCLVfteuniPv/pCWga/hUI0lfz1nhe0nNhAYnoxgsyFxX5QV2CIfylR6d6B7/WUUQHjcsCyiAjV/spyPFI8AFPZlhLsvjCVXOdP+EgAez6LeUZb0JEXZVohpl3BJmEOVJPfvKWXG9nsj5lpyi310lM3dwZIlT0qb7mVFZzFq6/qesc1E98CCEBbRufU7eTxgwLHsBdH091rXLHiQi4ul6apxiUAP/1qeFkNSEnoaqHNJwU74Bf9T+TndVVrX5ckHRlDl/Xz2PRQQgJpNJHAbqzHOooiYnw6 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: David Laight wrote: > > > Maybe you could use "%zu%c" and check the count is 1 - but I bet > > > some static checker won't like that. > > > > > > > Yes, that would be stronger, since it would reject trailing garbage. > > But for a selftest this is probably sufficient: switching to size_t and > > parsing with "%zu" already avoids the int truncation issue. > > Have you checked at what does sscanf() does with an overlong digit string? > I'd guess that it just processes all the digits and then masks the result > to fix (like the kernel one does). It will truncate the number to the size SIZE_MAX. >From my test: # ./write_to_hugetlbfs -m 0 -s 99999999999999999999999999 -p /mnt/huge/test -o Writing to this path: /mnt/huge/test Writing this size: 18446744073709551615 <---------- SIZE_MAX Populating. Not writing to memory. Using method=0 Shared mapping. RESERVE mapping. Allocating using HUGETLBFS. write_to_hugetlbfs: Error mapping the file: Invalid argument > It reality scanf() is 'not the function you are lookign for'. > > IIRC the 'SUS' (used to) say that this was absolutely fine for command > line parsing for 'standard utilities'. > > It is best to use strtoul() and check the 'end' character is '\0'. Hmm, that sounds like we need to go back to the patch V1 [1] method. But I am not sure, @Andrew Morton, do you think so? --- a/tools/testing/selftests/mm/write_to_hugetlbfs.c +++ b/tools/testing/selftests/mm/write_to_hugetlbfs.c @@ -86,10 +86,17 @@ int main(int argc, char **argv) while ((c = getopt(argc, argv, "s:p:m:owlrn")) != -1) { switch (c) { case 's': - if (sscanf(optarg, "%zu", &size) != 1) { - perror("Invalid -s."); + char *end = NULL; + unsigned long tmp = strtoul(optarg, &end, 10); + if (errno || end == optarg || *end != '\0') { + perror("Invalid -s size"); exit_usage(); } + if (tmp == 0) { + perror("size not found"); + exit_usage(); + } + size = (size_t)tmp; break; case 'p': [1] https://lore.kernel.org/linux-kselftest/20251220111645.2246009-3-liwang@redhat.com/T/#m5a5765349dedfda1ed66c54b8cab7af184bff371 -- Regards, Li Wang