Date: Thu, 5 Jan 2017 15:24:39 +0100
From: Matthieu Herrb <matthieu.herrb@laas.fr>
To: linux-nfs@vger.kernel.org
Subject: problem with open(name, O_RDWR|O_CREAT|O_EXCL, 0666) on NetApp
 servers
Message-ID: <20170105142439.GB9922@paperthin-usb.laas.fr>
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Hi,

After upgrading my machine to Ubuntu 16.04, I noticed that 'git clone'
started creating files with wrong mode (0700 instead of 0644
typically) on NFSv4 partitions mounted from our NetApp servers.

I've first tracked this down to the fact that git uses=20

 open(name, O_RDWR|O_CREAT|O_EXCL, 0666);

to create files. If O_EXCL is not present, the files are created
normally.

I've tried various kernels from Ubuntu and the problems appeared
between their 4.2.0-42-generic kernel-image (as found on willy) and
the 4.4.0 kernels found on xenial. I tried building 4.9 from
kernel.org and the problem is also there.

I've then bisected the kernel to figure out that this is caused by the
following commit:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=
=3D5334c5bdac926c5f8d89729beccb46fe88eda9e7

ie NFS: Send attributes in OPEN request for NFS4_CREATE_EXCLUSIVE4_1

Our NetApp filers are running:

NetApp Release 8.2.3P3 7-Mode: Tue Apr 28 14:48:22 PDT 2015

Any idea on how to fix the problem (either on the NetApp side, or on
Linux kernel side)?=20

Appended is a small program to reproduce the issue:

Thanks in advance,

#include <sys/types.h>
#include <sys/stat.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*
 * Demonstrate file creation bug on NFS v4 and linux kernel 4.4+
 *
 * mktemp() is used on purpose.
 */
int
main(int argc, char *argv[])
{
	const char *name =3D argv[1];
	char tmp[] =3D "./tmpXXXXXXXXXX";
	struct stat buf;
	mode_t expected;
	int fd, i, n =3D 40;

	umask(S_IWGRP | S_IWOTH);
	expected =3D 0666 & ~(S_IWGRP | S_IWOTH);
	if (argv[1] =3D=3D NULL)
		name =3D mktemp(tmp);
	for (i =3D 0; i < n; i++) {
		fd =3D open(name, O_RDWR|O_CREAT|O_EXCL, 0666);
		if (fd < 0)
			err(1, "open %s", name);
		memset(&buf, 0, sizeof(buf));
		if (stat(name, &buf) < 0)
			err(1, "stat %s", name);
		if ((buf.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) !=3D expected)
			printf("%s: %o\n", name,=20
			    (int)buf.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO));
		else
			printf("%s: ok\n", name);
		unlink(name);
	}
	exit(0);
}
--=20
Matthieu Herrb

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