On 12/4/18 10:02 PM, Dave Chinner wrote:
>
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> 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 <dchinner@xxxxxxxxxx>
whooops we crossed the streams :D
I'll move the man update to the file command section, but:
Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
> Version 2:
> - include a man page update from the new function
>
> io/open.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> man/man8/xfs_io.8 | 9 +++++++++
> 2 files changed, 63 insertions(+)
>
> diff --git a/io/open.c b/io/open.c
> index 21c0e054f8d2..2663c38e9681 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");
> + 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);
> }
> diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
> index f1099c32de66..68e03b4558b9 100644
> --- a/man/man8/xfs_io.8
> +++ b/man/man8/xfs_io.8
> @@ -1226,6 +1226,15 @@ characters long.
> .B crc32cselftest
> Test the internal crc32c implementation to make sure that it computes results
> correctly.
> +.TP
> +.B chmod \-r | \-w
> +Change the mode of the currently open file. The
> +.B \-r
> +option will set the file permissions to read-only (0444), whilst the
> +.B \-w
> +option will set the file permissions to read-write (0644). This allows xfs_io to
> +set up mismatches between the file permissions and the open file descriptor
> +read/write mode to exercise permission checks inside various syscalls.
> .SH SEE ALSO
> .BR mkfs.xfs (8),
> .BR xfsctl (3),
>
