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Full Discussion: /dev/null file issue
Operating Systems AIX /dev/null file issue Post 302772456 by MichaelFelt on Monday 25th of February 2013 05:01:25 PM
Old 02-25-2013
I think a more AIX way of recreating /dev/null on AIX is:

Code:
# rm /dev/null
# cfgmgr

I would be curious to know how it became a character file (implies someone with write perms on /dev removed it, and the first person to write to /dev/null (would be the new owner) recreated it as a regular file. I would expect that there is a script being run by root that is deleting it, and writing it again. Since you show 0 bytes, it is also being truncated as well.

So, your second security issue is when is it being removed? If you cannot answer this, the issue will come back and haunt you.
This User Gave Thanks to MichaelFelt For This Post:
jayadeava
 

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LEARN ABOUT X11R4

mem

MEM(4)                                                       Linux Programmer's Manual                                                      MEM(4)

NAME

       mem, kmem, port - system memory, kernel memory and system ports

DESCRIPTION

       /dev/mem is a character device file that is an image of the main memory of the computer.  It may be used, for example, to examine (and even
       patch) the system.

       Byte addresses in /dev/mem are interpreted as physical memory addresses.  References to nonexistent locations cause errors to be returned.

       Examining and patching is likely to lead to unexpected results when read-only or write-only bits are present.

       Since Linux 2.6.26, and depending on the architecture, the CONFIG_STRICT_DEVMEM kernel configuration option limits the areas which  can  be
       accessed through this file.  For example: on x86, RAM access is not allowed but accessing memory-mapped PCI regions is.

       It is typically created by:

           mknod -m 660 /dev/mem c 1 1
           chown root:kmem /dev/mem

       The  file  /dev/kmem  is  the same as /dev/mem, except that the kernel virtual memory rather than physical memory is accessed.  Since Linux
       2.6.26, this file is available only if the CONFIG_DEVKMEM kernel configuration option is enabled.

       It is typically created by:

           mknod -m 640 /dev/kmem c 1 2
           chown root:kmem /dev/kmem

       /dev/port is similar to /dev/mem, but the I/O ports are accessed.

       It is typically created by:

           mknod -m 660 /dev/port c 1 4
           chown root:kmem /dev/port

FILES

       /dev/mem
       /dev/kmem
       /dev/port

SEE ALSO

       chown(1), mknod(1), ioperm(2)

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux                                                               2015-01-02                                                              MEM(4)
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