man > proc_pid_attr(5)

proc_pid_attr(5)                         File Formats Manual                        proc_pid_attr(5)

NAME
       /proc/pid/attr/ - security-related attributes

DESCRIPTION
       /proc/pid/attr/
              The files in this directory provide an API for security modules.  The contents of this
              directory  are files that can be read and written in order to set security-related at‐
              tributes.  This directory was added to support SELinux, but the intention was that the
              API be general enough to support other security modules.  For the purpose of  explana‐
              tion, examples of how SELinux uses these files are provided below.

              This directory is present only if the kernel was configured with CONFIG_SECURITY.

       /proc/pid/attr/current (since Linux 2.6.0)
              The contents of this file represent the current security attributes of the process.

              In  SELinux,  this  file  is  used to get the security context of a process.  Prior to
              Linux 2.6.11, this file could not be used to set the security context (a write was al‐
              ways denied), since SELinux limited process security transitions to execve(2) (see the
              description of /proc/pid/attr/exec, below).  Since Linux 2.6.11, SELinux  lifted  this
              restriction  and  began  supporting "set" operations via writes to this node if autho‐
              rized by policy, although use of this operation is only suitable for applications that
              are trusted to maintain any desired separation between the old and new  security  con‐
              texts.

              Prior to Linux 2.6.28, SELinux did not allow threads within a multithreaded process to
              set  their security context via this node as it would yield an inconsistency among the
              security contexts of the threads sharing the same memory space.  Since  Linux  2.6.28,
              SELinux  lifted  this  restriction  and  began supporting "set" operations for threads
              within a multithreaded process if the new security context is bounded by the old secu‐
              rity context, where the bounded relation is defined in policy and guarantees that  the
              new security context has a subset of the permissions of the old security context.

              Other security modules may choose to support "set" operations via writes to this node.

       /proc/pid/attr/exec (since Linux 2.6.0)
              This  file  represents  the  attributes to assign to the process upon a subsequent ex‐
              ecve(2).

              In SELinux, this is needed to support role/domain transitions, and  execve(2)  is  the
              preferred  point  to  make  such transitions because it offers better control over the
              initialization of the process in the new security label and the inheritance of  state.
              In  SELinux,  this  attribute is reset on execve(2) so that the new program reverts to
              the default behavior for any execve(2) calls that it may make.  In SELinux, a  process
              can set only its own /proc/pid/attr/exec attribute.

       /proc/pid/attr/fscreate (since Linux 2.6.0)
              This  file represents the attributes to assign to files created by subsequent calls to
              open(2), mkdir(2), symlink(2), and mknod(2)

              SELinux employs this file to support creation of a file (using the aforementioned sys‐
              tem calls) in a secure state, so that there is no risk of inappropriate  access  being
              obtained  between  the  time  of  creation  and  the time that attributes are set.  In
              SELinux, this attribute is reset on execve(2), so that the new program reverts to  the
              default  behavior for any file creation calls it may make, but the attribute will per‐
              sist across multiple file creation calls within a program unless it is explicitly  re‐
              set.  In SELinux, a process can set only its own /proc/pid/attr/fscreate attribute.

       /proc/pid/attr/keycreate (since Linux 2.6.18)
              If  a  process writes a security context into this file, all subsequently created keys
              (add_key(2)) will be labeled with this context.  For further information, see the ker‐
              nel source  file  Documentation/security/keys/core.rst  (or  file  Documentation/secu‐
              rity/keys.txt between Linux 3.0 and Linux 4.13, or Documentation/keys.txt before Linux
              3.0).

       /proc/pid/attr/prev (since Linux 2.6.0)
              This file contains the security context of the process before the last execve(2); that
              is, the previous value of /proc/pid/attr/current.

       /proc/pid/attr/socketcreate (since Linux 2.6.18)
              If  a process writes a security context into this file, all subsequently created sock‐
              ets will be labeled with this context.

SEE ALSO
       proc(5)

Linux man-pages 6.7                          2023-08-15                             proc_pid_attr(5)