From: ludo@gnu.org (Ludovic Courtès)
To: 24659@debbugs.gnu.org
Subject: bug#24659: 'mkdir' procedure is neither thread-safe nor safe (2.0.12)
Date: Mon, 10 Oct 2016 18:39:47 +0200 [thread overview]
Message-ID: <87pon8ma3w.fsf@gnu.org> (raw)
Hello!
When the optional ‘mode’ argument to the ‘mkdir’ procedure is omitted,
umask(2) is used to find out what the current mask is and to compute the
mode argument to mkdir(2):
--8<---------------cut here---------------start------------->8---
if (SCM_UNBNDP (mode))
{
mask = umask (0);
umask (mask);
STRING_SYSCALL (path, c_path, rv = mkdir (c_path, 0777 ^ mask));
}
--8<---------------cut here---------------end--------------->8---
The problem is that this changes the process’ umask globally for a short
duration, during which other threads will get 0 as the mask…
Furthermore, AFAICS, the above logic is redundant with what the kernel
does anyway. That is, in a single-threaded program,
mask = umask (0);
umask (mask);
mkdir (file, 0777 ^ mask);
is equivalent to:
mkdir (file, 0777);
Am I right that we should just remove these two ‘umask’ calls?
Ludo’.
PS: This code has been there since 1996 or earlier.
next reply other threads:[~2016-10-10 16:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-10 16:39 Ludovic Courtès [this message]
2016-10-10 18:25 ` bug#24659: 'mkdir' procedure is neither thread-safe nor safe (2.0.12) tomas
2016-10-11 9:13 ` Ludovic Courtès
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