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b=08/+s6Qcq4HVi/H4W3MD2fJtmg7A9T0b0dpAdF6cTj998kxZ05Wn5oTdiktIwlApz 0EchykW636s6Lpq0OHCtMt0h4Wp27k4JHqqKiipg8mEBrTJZ4AeuriGkskTQYloVrd Mo7nYwxl7wCG5hi5yvisMSx9xRVdadUMOkYeiQ0s= Date: Sat, 20 Dec 2025 10:58:11 -0800 From: Andrew Morton To: Li Wang Cc: linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand , Mark Brown , Shuah Khan , Waiman Long Subject: Re: [PATCH 1/3] selftests/mm/write_to_hugetlbfs: parse -s with strtoull and use size_t Message-Id: <20251220105811.3516167661cd696f464cc3b0@linux-foundation.org> In-Reply-To: <20251220111645.2246009-2-liwang@redhat.com> References: <20251220111645.2246009-1-liwang@redhat.com> <20251220111645.2246009-2-liwang@redhat.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 2170780006 X-Stat-Signature: sgtmng5id94t4nyezro9bzqoznsj57zk X-HE-Tag: 1766257093-827944 X-HE-Meta: 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 VcbnUwXy mss5D8TNFzQiienneo2xlt83mf66PBYZXDdW0Rmtv/VNInpOkUy733CCWka+ox5KTxzhEvUqH6gMyD68KkeOBkLC5srJZJs1wxzWzhyN9eml5iHpN5V92o/xJuGKq4/0Qx/e4/jZ0Vya+DrVPzdadKLBETfkrLx+cmPVAzDXaAHQ0Xdfhl1Hrn6i3FCC1M9iDB6hgbTNhVx0CWr1/XdRnNV4YoszDXC400Y9LH7fg6zZWqGY0J5gB9HUlrRW79wNCshMr+BeX9EXObFyVU7+BhmslIX2EOAFEy78dpoS1VuHPA/Cj1klTYpajW/oFUZfuIk2n 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: On Sat, 20 Dec 2025 19:16:43 +0800 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 Can we fix that typo while we're in there? "reservation". > ... > # Writing to this path: /mnt/huge/test > # Writing this size: -1610612736 <-------- > > Switch size to size_t and parse -s using strtoull() with proper validation. > Also print the size using %zu. > > This makes the test utility more robust and avoids undefined/incorrect > behavior with large or invalid -s values. > > ... > > --- 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 +86,20 @@ int main(int argc, char **argv) > while ((c = getopt(argc, argv, "s:p:m:owlrn")) != -1) { > switch (c) { > case 's': > - size = atoi(optarg); > + errno = 0; > + char *end = NULL; > + unsigned long long tmp = strtoull(optarg, &end, 10); Coding-style nits: we do accept c99-style definitions nowadays but I do think our eyes prefer the less surprising "definitions come before code" style. So the above could be char *end = NULL; unsigned long long tmp = strtoull(optarg, &end, 10); errno = 0; Also, `errno' belongs to libc. It seems wrong to be altering it from within our client code. > + if (errno || end == optarg || *end != '\0') { > + errno = EINVAL; > + perror("Invalid -s size"); > + exit_usage(); > + } > + if (tmp == 0) { > + errno = EINVAL; > + perror("size not found"); > + exit_usage(); > + } > + size = (size_t)tmp; > break; I'm not really clear on what problems we're trying to solve here, but this all seems like a lot of fuss. Can we just do if (sscanf(optarg, "%zu", &size) != 1) ? > case 'p': > strncpy(path, optarg, sizeof(path) - 1); > @@ -131,7 +144,7 @@ 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");