diff mbox series

[2/2,V2] xfs_io: allow open file permissions to be changed

Message ID 20181205040226.GS6311@dastard (mailing list archive)
State Accepted, archived
Headers show
Series None | expand

Commit Message

Dave Chinner Dec. 5, 2018, 4:02 a.m. UTC 
From: Dave Chinner <dchinner@redhat.com>

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@redhat.com>
---
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(+)

Comments

Eric Sandeen Dec. 5, 2018, 4:23 a.m. UTC | #1 
On 12/4/18 10:02 PM, Dave Chinner wrote:
> 
> From: Dave Chinner <dchinner@redhat.com>
> 
> 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@redhat.com>

whooops we crossed the streams :D

I'll move the man update to the file command section, but:

Reviewed-by: Eric Sandeen <sandeen@redhat.com>

> ---
> 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),
>
diff mbox series

Patch

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),