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([2601:600:947f:f020:85dc:d2b2:c5ee:e3c4]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-88d96bec1d3sm66333926d6.17.2025.12.21.12.23.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 21 Dec 2025 12:23:25 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <39c9af10-d66f-4bcc-93a6-9e2d33827938@redhat.com> Date: Sun, 21 Dec 2025 15:23:22 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as size_t To: Li Wang , akpm@linux-foundation.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: David Hildenbrand , Mark Brown , Shuah Khan References: <20251221122639.3168038-1-liwang@redhat.com> <20251221122639.3168038-2-liwang@redhat.com> Content-Language: en-US In-Reply-To: <20251221122639.3168038-2-liwang@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/21/25 7:26 AM, Li Wang wrote: > write_to_hugetlbfs currently parses the -s size argument with atoi() > into an int. This silently accepts malformed input, cannot report overflow, > and can truncate large sizes. > > --- Error log --- > # uname -r > 6.12.0-xxx.el10.aarch64+64k > > # ls /sys/kernel/mm/hugepages/hugepages-* > hugepages-16777216kB/ hugepages-2048kB/ hugepages-524288kB/ > > #./charge_reserved_hugetlb.sh -cgroup-v2 > # ----------------------------------------- > ... > # nr hugepages = 10 > # writing cgroup limit: 5368709120 > # writing reseravation limit: 5368709120 > ... > # Writing to this path: /mnt/huge/test > # Writing this size: -1610612736 <-------- > > Switch the size variable to size_t and parse -s with sscanf("%zu", ...). > Also print the size using %zu. > > This avoids incorrect behavior with large -s values and makes the utility > more robust. > > Signed-off-by: Li Wang > Cc: David Hildenbrand > Cc: Mark Brown > Cc: Shuah Khan > Cc: Waiman Long > Acked-by: David Hildenbrand (Red Hat) > --- > tools/testing/selftests/mm/write_to_hugetlbfs.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/tools/testing/selftests/mm/write_to_hugetlbfs.c b/tools/testing/selftests/mm/write_to_hugetlbfs.c > index 34c91f7e6128..ecb5f7619960 100644 > --- a/tools/testing/selftests/mm/write_to_hugetlbfs.c > +++ b/tools/testing/selftests/mm/write_to_hugetlbfs.c > @@ -68,7 +68,7 @@ int main(int argc, char **argv) > int key = 0; > int *ptr = NULL; > int c = 0; > - int size = 0; > + size_t size = 0; > char path[256] = ""; > enum method method = MAX_METHOD; > int want_sleep = 0, private = 0; > @@ -86,7 +86,10 @@ int main(int argc, char **argv) > while ((c = getopt(argc, argv, "s:p:m:owlrn")) != -1) { > switch (c) { > case 's': > - size = atoi(optarg); > + if (sscanf(optarg, "%zu", &size) != 1) { > + perror("Invalid -s."); > + exit_usage(); > + } > break; > case 'p': > strncpy(path, optarg, sizeof(path) - 1); > @@ -131,7 +134,7 @@ int main(int argc, char **argv) > } > > if (size != 0) { > - printf("Writing this size: %d\n", size); > + printf("Writing this size: %zu\n", size); > } else { > errno = EINVAL; > perror("size not found"); LGTM Acked-by: Waiman Long