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Bug 1182463

Summary: "mknod-b", "mknod-c", and "mkfifo" do not strip non-permissions bits from "mode"
Product: Red Hat Enterprise Linux 7 Reporter: Chao Zhang <chazhang>
Component: libguestfsAssignee: Richard W.M. Jones <rjones>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: low Docs Contact:
Priority: unspecified    
Version: 7.1CC: huzhan, leiwang, mbooth, ptoscano, wshi
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: libguestfs-1.28.1-1.25.el7 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2015-11-19 06:59:26 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Chao Zhang 2015-01-15 07:50:49 UTC
Description of problem:
The way libguestfs handle "mode" in "mknod-b" "mknod-c" "mkfifo" have some bugs.

The source code are:

int
do_mkfifo (int mode, const char *path)
{
  return do_mknod (mode | S_IFIFO, 0, 0, path);
}

int
do_mknod_b (int mode, int devmajor, int devminor, const char *path)
{
  return do_mknod (mode | S_IFBLK, devmajor, devminor, path);
}

int
do_mknod_c (int mode, int devmajor, int devminor, const char *path)
{
  return do_mknod (mode | S_IFCHR, devmajor, devminor, path);
}

/usr/include/bits/stat.h
#define __S_IFCHR   0020000 /* Character device.  */
#define __S_IFBLK   0060000 /* Block device.  */
#define __S_IFIFO   0010000 /* FIFO.  */

"mknod-c 0060XXX" == "mknod 0060XXX", In this case, "mknod-c" will create a block device.
"mkfifo 0000XXX" == "mkfifo 0010XXX", In this case, returning an error would be better.

Version-Release number of selected component (if applicable):
libguestfs-tools-c-1.28.1-1.17.el7.x86_64

How reproducible:
100%


Steps to Reproduce:
1. create a img, and add the img
# guestfish -N fs:ext3

2. use mknod, mknod-b, mknod-c to create device
><fs> mknod-c 0060777 8 1 /test_mknod_c
><fs> mkfifo 0000777 /test_mkfifo
><fs> ll /
total 17
drwxr-xr-x  3 root root  1024 Jan 15 04:29 .
drwxr-xr-x 19 root root  4096 Jan 15 03:40 ..
drwx------  2 root root 12288 Jan 15 03:41 lost+found
prwxr-xr-x  1 root root     0 Jan 15 04:29 test_mkfifo
brwxr-xr-x  1 root root  8, 1 Jan 15 04:28 test_mknod_c


Actual results:
mknod-c create a block device, and mkfifo create a fifo device when given a wrong mode.


Expected results:
If the mode doesn't match the device mode, libguestfs returns an "Invalid argument" error.


Additional info:
...

Comment 1 Pino Toscano 2015-01-15 13:47:24 UTC
As you can see and it is also documented, "mknod-b", "mknod-c", and "mkfifo" are just wrappers to "mknod", just adding the bit for the node type (block device, character device, fifo).
If they are used correctly, i.e. just passing permissions as mode, they behave as described, so I don't consider this a big issue.

In any case, patch posted:
  https://www.redhat.com/archives/libguestfs/2015-January/msg00040.html

Comment 5 Hu Zhang 2015-05-06 05:25:37 UTC
Verified with libguestfs-1.28.1-1.29.el7

Steps to verify:
1. use mknod, mknod-b, mknod-c to create device
><fs> mknod-c 0060777 8 1 /test_mknod_c
mknod-c 0060777 8 1 /test_mknod_c
libguestfs: error: mknod_c: 60777: mode must specify only file permission bits
><fs> mknod-b 0060777 8 1 /test_mknod_b
libguestfs: error: mknod_b: 60777: mode must specify only file permission bits
><fs> mkfifo 0010777 /test_mkfifo
libguestfs: error: mkfifo: 10777: mode must specify only file permission bits

><fs> mknod-c 0777 8 1 /test_mknod_c
><fs> mknod-b 0777 8 1 /test_mknod_b
><fs> mkfifo 0777 /test_mkfifo
><fs> ll /
prwxr-xr-x   1 root root        0 May  6 05:22 test_mkfifo
brwxr-xr-x   1 root root     8, 1 May  6 05:22 test_mknod_b
crwxr-xr-x   1 root root     8, 1 May  6 05:18 test_mknod_c

It pops up an error when the mode includes non-permissions bits. So fixed.

Comment 7 errata-xmlrpc 2015-11-19 06:59:26 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2183.html