From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp2130.oracle.com ([156.151.31.86]:58738 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726560AbeLCQYV (ORCPT ); Mon, 3 Dec 2018 11:24:21 -0500 Date: Mon, 3 Dec 2018 08:24:11 -0800 From: "Darrick J. Wong" Subject: Re: [PATCH 2/2] xfs_io: allow open file permissions to be changed Message-ID: <20181203162411.GU8125@magnolia> References: <20181202205343.7104-1-david@fromorbit.com> <20181202205343.7104-3-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181202205343.7104-3-david@fromorbit.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Dave Chinner Cc: linux-xfs@vger.kernel.org On Mon, Dec 03, 2018 at 07:53:43AM +1100, Dave Chinner wrote: > From: Dave Chinner > > I need to be able to open a file read-write, then change the > permissions on the file to read-only to check that copy_file_range > returns EPERM correctly in that case. This can't be done as root, > because root ignores file permissions, but as a normal user we can't > open a 0444 file for writing and so can't actually test writing to > a read-only file without some method of "open read-write, change > permissions to read-only, try to write to file through open > read-write file". > > So, allow adding or removing write permissions on an open file. > > Signed-off-by: Dave Chinner > --- > io/open.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 54 insertions(+) > > diff --git a/io/open.c b/io/open.c > index b1d9a0fa317c..153d4a836d4c 100644 > --- a/io/open.c > +++ b/io/open.c > @@ -44,6 +44,7 @@ static cmdinfo_t chproj_cmd; > static cmdinfo_t lsproj_cmd; > static cmdinfo_t extsize_cmd; > static cmdinfo_t inode_cmd; > +static cmdinfo_t chmod_cmd; > static prid_t prid; > static long extsize; > > @@ -809,6 +810,48 @@ inode_f( > return 0; > } > > +static void > +chmod_help(void) > +{ > + printf(_( > +"\n" > +" Change the read/write permissions on the current file\n" > +"\n" > +" Options:\n" > +" -r -- make the file read only (0444 permissions)\n" > +" -w -- make the file read/write (0664 permissions)\n" > +"\n")); > +} > + > +static int > +chmod_f( > + int argc, > + char **argv) > +{ > + mode_t mode = S_IRUSR | S_IRGRP | S_IROTH; > + int c; > + > + while ((c = getopt(argc, argv, "rw")) != EOF) { > + switch (c) { > + case 'r': > + break; > + case 'w': > + mode |= S_IWUSR | S_IWGRP; > + break; > + default: > + return command_usage(&chmod_cmd); > + } > + } > + > + if (argc != optind) > + return command_usage(&chmod_cmd); > + > + if (fchmod(file->fd, mode) < 0) { > + exitcode = 1; > + perror("fchmod"); > + } > + return 0; > +} > void > open_init(void) > { > @@ -871,10 +914,21 @@ open_init(void) > _("Query inode number usage in the filesystem"); > inode_cmd.help = inode_help; > > + chmod_cmd.name = "chmod"; > + chmod_cmd.cfunc = chmod_f; > + chmod_cmd.args = _("-r | -w"); > + chmod_cmd.argmin = 1; > + chmod_cmd.argmax = 1; > + chmod_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK | CMD_FLAG_ONESHOT; > + chmod_cmd.oneline = > + _("change the read/write permissios on the currently open file"); "permissions"... Also, there needs to be a manpage update for this, or else xfs/293 fails. --D > + chmod_cmd.help = chmod_help; > + > add_command(&open_cmd); > add_command(&close_cmd); > add_command(&chproj_cmd); > add_command(&lsproj_cmd); > add_command(&extsize_cmd); > add_command(&inode_cmd); > + add_command(&chmod_cmd); > } > -- > 2.19.1 >