Re: [PATCH] linux: sysconf: limit _SC_MAX_ARG to 6 MiB [BZ #25305]

[Andreas Schwab <schwab@linux-m68k.org>]

On Apr 12 2021, Michal Nazarewicz wrote:

>> On 07/04/2021 12:10, Michal Nazarewicz wrote:
>>> Since Linux 4.13, kernel limits the maximum command line arguments
>>> length to 6 MiB.¹  Normally the limit is still quarter of the maximum
>>> stack size but if that limit exceeds 6 MiB it’s clamped down.
>
> On Mon, Apr 12 2021, Adhemerval Zanella wrote:
>> Patch look good to me, thanks.
>>
>> Reviewed=by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
>>
>>> ---
>>>  sysdeps/unix/sysv/linux/sysconf.c | 5 ++++-
>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>> 
>>> 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) == 0)
>>> -	  return MAX (legacy_ARG_MAX, rlimit.rlim_cur / 4);
>>> +	  {
>>> +	    const long int limit = 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’d rather go with ‘6 * 1024 * 1024’ if shifts aren’t readable.

In addition, I'd give it a symbolic name with a comment.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
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