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[213.238.124.172]) by smtp.gmail.com with ESMTPSA id o11sm3110825ljg.42.2021.04.12.14.31.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Apr 2021 14:31:20 -0700 (PDT) Sender: =?UTF-8?Q?Micha=C5=82_Nazarewicz?= From: Michal Nazarewicz To: Adhemerval Zanella , libc-alpha@sourceware.org Subject: Re: [PATCH] linux: sysconf: limit _SC_MAX_ARG to 6 MiB [BZ #25305] In-Reply-To: <46c3ea60-7a57-14f7-92f9-e915e3b12dae@linaro.org> References: <20210407151058.1176364-1-mina86@mina86.com> <46c3ea60-7a57-14f7-92f9-e915e3b12dae@linaro.org> Face: 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 Date: Mon, 12 Apr 2021 23:31:19 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-6.6 required=5.0 tests=BAYES_00, BODY_8BITS, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_EF, FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM, GIT_PATCH_0, HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_BARRACUDACENTRAL, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 12 Apr 2021 21:31:24 -0000 > On 07/04/2021 12:10, Michal Nazarewicz wrote: >> Since Linux 4.13, kernel limits the maximum command line arguments >> length to 6 MiB.=C2=B9 Normally the limit is still quarter of the maxim= um >> stack size but if that limit exceeds 6 MiB it=E2=80=99s clamped down. On Mon, Apr 12 2021, Adhemerval Zanella wrote: > Patch look good to me, thanks. > > Reviewed=3Dby: Adhemerval Zanella > >> --- >> sysdeps/unix/sysv/linux/sysconf.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >>=20 >> diff --git a/sysdeps/unix/sysv/linux/sysconf.c b/sysdeps/unix/sysv/linux= /sysconf.c >> index 366fcef01e..bd711795c7 100644 >> --- a/sysdeps/unix/sysv/linux/sysconf.c >> +++ b/sysdeps/unix/sysv/linux/sysconf.c >> @@ -55,7 +55,10 @@ __sysconf (int name) >> struct rlimit rlimit; >> /* Use getrlimit to get the stack limit. */ >> if (__getrlimit (RLIMIT_STACK, &rlimit) =3D=3D 0) >> - return MAX (legacy_ARG_MAX, rlimit.rlim_cur / 4); >> + { >> + const long int limit =3D MAX (legacy_ARG_MAX, rlimit.rlim_cur / 4); >> + return MIN (limit, 6 << 10 << 10); > > I think it a bit easier to read with the value expanded (6291456). I=E2=80=99d rather go with =E2=80=986 * 1024 * 1024=E2=80=99 if shifts aren= =E2=80=99t readable. >> + } >>=20=20 >> return legacy_ARG_MAX; >> } >>=20 --=20 Best regards =E3=83=9F=E3=83=8F=E3=82=A6 =E2=80=9C=F0=9D=93=B6=F0=9D=93=B2=F0=9D=93=B7= =F0=9D=93=AA86=E2=80=9D =E3=83=8A=E3=82=B6=E3=83=AC=E3=83=B4=E3=82=A4=E3=83= =84 =C2=ABIf at first you don=E2=80=99t succeed, give up skydiving=C2=BB