1. 21 Aug, 2009 1 commit
    • Amerigo Wang's avatar
      vfs: allow file truncations when both suid and write permissions set · 939a9421
      Amerigo Wang authored
      When suid is set and the non-owner user has write permission, any writing
      into this file should be allowed and suid should be removed after that.
      
      However, current kernel only allows writing without truncations, when we
      do truncations on that file, we get EPERM.  This is a bug.
      
      Steps to reproduce this bug:
      
      % ls -l rootdir/file1
      -rwsrwsrwx 1 root root 3 Jun 25 15:42 rootdir/file1
      % echo h > rootdir/file1
      zsh: operation not permitted: rootdir/file1
      % ls -l rootdir/file1
      -rwsrwsrwx 1 root root 3 Jun 25 15:42 rootdir/file1
      % echo h >> rootdir/file1
      % ls -l rootdir/file1
      -rwxrwxrwx 1 root root 5 Jun 25 16:34 rootdir/file1
      Signed-off-by: default avatarWANG Cong <amwang@redhat.com>
      Cc: Eric Sandeen <esandeen@redhat.com>
      Acked-by: default avatarEric Paris <eparis@redhat.com>
      Cc: Eugene Teo <eteo@redhat.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Stephen Smalley <sds@tycho.nsa.gov>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      939a9421
  2. 24 Jun, 2009 1 commit
  3. 12 Jun, 2009 1 commit
    • npiggin@suse.de's avatar
      fs: introduce mnt_clone_write · 96029c4e
      npiggin@suse.de authored
      This patch speeds up lmbench lat_mmap test by about another 2% after the
      first patch.
      
      Before:
       avg = 462.286
       std = 5.46106
      
      After:
       avg = 453.12
       std = 9.58257
      
      (50 runs of each, stddev gives a reasonable confidence)
      
      It does this by introducing mnt_clone_write, which avoids some heavyweight
      operations of mnt_want_write if called on a vfsmount which we know already
      has a write count; and mnt_want_write_file, which can call mnt_clone_write
      if the file is open for write.
      
      After these two patches, mnt_want_write and mnt_drop_write go from 7% on
      the profile down to 1.3% (including mnt_clone_write).
      
      [AV: mnt_want_write_file() should take file alone and derive mnt from it;
      not only all callers have that form, but that's the only mnt about which
      we know that it's already held for write if file is opened for write]
      
      Cc: Dave Hansen <haveblue@us.ibm.com>
      Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      96029c4e
  4. 09 May, 2009 1 commit
  5. 01 Apr, 2009 1 commit
  6. 26 Mar, 2009 1 commit
  7. 14 Jan, 2009 9 commits
  8. 05 Jan, 2009 1 commit
    • Al Viro's avatar
      inode->i_op is never NULL · acfa4380
      Al Viro authored
      We used to have rather schizophrenic set of checks for NULL ->i_op even
      though it had been eliminated years ago.  You'd need to go out of your
      way to set it to NULL explicitly _and_ a bunch of code would die on
      such inodes anyway.  After killing two remaining places that still
      did that bogosity, all that crap can go away.
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      acfa4380
  9. 31 Dec, 2008 1 commit
  10. 13 Nov, 2008 4 commits
    • David Howells's avatar
      CRED: Inaugurate COW credentials · d84f4f99
      David Howells authored
      Inaugurate copy-on-write credentials management.  This uses RCU to manage the
      credentials pointer in the task_struct with respect to accesses by other tasks.
      A process may only modify its own credentials, and so does not need locking to
      access or modify its own credentials.
      
      A mutex (cred_replace_mutex) is added to the task_struct to control the effect
      of PTRACE_ATTACHED on credential calculations, particularly with respect to
      execve().
      
      With this patch, the contents of an active credentials struct may not be
      changed directly; rather a new set of credentials must be prepared, modified
      and committed using something like the following sequence of events:
      
      	struct cred *new = prepare_creds();
      	int ret = blah(new);
      	if (ret < 0) {
      		abort_creds(new);
      		return ret;
      	}
      	return commit_creds(new);
      
      There are some exceptions to this rule: the keyrings pointed to by the active
      credentials may be instantiated - keyrings violate the COW rule as managing
      COW keyrings is tricky, given that it is possible for a task to directly alter
      the keys in a keyring in use by another task.
      
      To help enforce this, various pointers to sets of credentials, such as those in
      the task_struct, are declared const.  The purpose of this is compile-time
      discouragement of altering credentials through those pointers.  Once a set of
      credentials has been made public through one of these pointers, it may not be
      modified, except under special circumstances:
      
        (1) Its reference count may incremented and decremented.
      
        (2) The keyrings to which it points may be modified, but not replaced.
      
      The only safe way to modify anything else is to create a replacement and commit
      using the functions described in Documentation/credentials.txt (which will be
      added by a later patch).
      
      This patch and the preceding patches have been tested with the LTP SELinux
      testsuite.
      
      This patch makes several logical sets of alteration:
      
       (1) execve().
      
           This now prepares and commits credentials in various places in the
           security code rather than altering the current creds directly.
      
       (2) Temporary credential overrides.
      
           do_coredump() and sys_faccessat() now prepare their own credentials and
           temporarily override the ones currently on the acting thread, whilst
           preventing interference from other threads by holding cred_replace_mutex
           on the thread being dumped.
      
           This will be replaced in a future patch by something that hands down the
           credentials directly to the functions being called, rather than altering
           the task's objective credentials.
      
       (3) LSM interface.
      
           A number of functions have been changed, added or removed:
      
           (*) security_capset_check(), ->capset_check()
           (*) security_capset_set(), ->capset_set()
      
           	 Removed in favour of security_capset().
      
           (*) security_capset(), ->capset()
      
           	 New.  This is passed a pointer to the new creds, a pointer to the old
           	 creds and the proposed capability sets.  It should fill in the new
           	 creds or return an error.  All pointers, barring the pointer to the
           	 new creds, are now const.
      
           (*) security_bprm_apply_creds(), ->bprm_apply_creds()
      
           	 Changed; now returns a value, which will cause the process to be
           	 killed if it's an error.
      
           (*) security_task_alloc(), ->task_alloc_security()
      
           	 Removed in favour of security_prepare_creds().
      
           (*) security_cred_free(), ->cred_free()
      
           	 New.  Free security data attached to cred->security.
      
           (*) security_prepare_creds(), ->cred_prepare()
      
           	 New. Duplicate any security data attached to cred->security.
      
           (*) security_commit_creds(), ->cred_commit()
      
           	 New. Apply any security effects for the upcoming installation of new
           	 security by commit_creds().
      
           (*) security_task_post_setuid(), ->task_post_setuid()
      
           	 Removed in favour of security_task_fix_setuid().
      
           (*) security_task_fix_setuid(), ->task_fix_setuid()
      
           	 Fix up the proposed new credentials for setuid().  This is used by
           	 cap_set_fix_setuid() to implicitly adjust capabilities in line with
           	 setuid() changes.  Changes are made to the new credentials, rather
           	 than the task itself as in security_task_post_setuid().
      
           (*) security_task_reparent_to_init(), ->task_reparent_to_init()
      
           	 Removed.  Instead the task being reparented to init is referred
           	 directly to init's credentials.
      
      	 NOTE!  This results in the loss of some state: SELinux's osid no
      	 longer records the sid of the thread that forked it.
      
           (*) security_key_alloc(), ->key_alloc()
           (*) security_key_permission(), ->key_permission()
      
           	 Changed.  These now take cred pointers rather than task pointers to
           	 refer to the security context.
      
       (4) sys_capset().
      
           This has been simplified and uses less locking.  The LSM functions it
           calls have been merged.
      
       (5) reparent_to_kthreadd().
      
           This gives the current thread the same credentials as init by simply using
           commit_thread() to point that way.
      
       (6) __sigqueue_alloc() and switch_uid()
      
           __sigqueue_alloc() can't stop the target task from changing its creds
           beneath it, so this function gets a reference to the currently applicable
           user_struct which it then passes into the sigqueue struct it returns if
           successful.
      
           switch_uid() is now called from commit_creds(), and possibly should be
           folded into that.  commit_creds() should take care of protecting
           __sigqueue_alloc().
      
       (7) [sg]et[ug]id() and co and [sg]et_current_groups.
      
           The set functions now all use prepare_creds(), commit_creds() and
           abort_creds() to build and check a new set of credentials before applying
           it.
      
           security_task_set[ug]id() is called inside the prepared section.  This
           guarantees that nothing else will affect the creds until we've finished.
      
           The calling of set_dumpable() has been moved into commit_creds().
      
           Much of the functionality of set_user() has been moved into
           commit_creds().
      
           The get functions all simply access the data directly.
      
       (8) security_task_prctl() and cap_task_prctl().
      
           security_task_prctl() has been modified to return -ENOSYS if it doesn't
           want to handle a function, or otherwise return the return value directly
           rather than through an argument.
      
           Additionally, cap_task_prctl() now prepares a new set of credentials, even
           if it doesn't end up using it.
      
       (9) Keyrings.
      
           A number of changes have been made to the keyrings code:
      
           (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have
           	 all been dropped and built in to the credentials functions directly.
           	 They may want separating out again later.
      
           (b) key_alloc() and search_process_keyrings() now take a cred pointer
           	 rather than a task pointer to specify the security context.
      
           (c) copy_creds() gives a new thread within the same thread group a new
           	 thread keyring if its parent had one, otherwise it discards the thread
           	 keyring.
      
           (d) The authorisation key now points directly to the credentials to extend
           	 the search into rather pointing to the task that carries them.
      
           (e) Installing thread, process or session keyrings causes a new set of
           	 credentials to be created, even though it's not strictly necessary for
           	 process or session keyrings (they're shared).
      
      (10) Usermode helper.
      
           The usermode helper code now carries a cred struct pointer in its
           subprocess_info struct instead of a new session keyring pointer.  This set
           of credentials is derived from init_cred and installed on the new process
           after it has been cloned.
      
           call_usermodehelper_setup() allocates the new credentials and
           call_usermodehelper_freeinfo() discards them if they haven't been used.  A
           special cred function (prepare_usermodeinfo_creds()) is provided
           specifically for call_usermodehelper_setup() to call.
      
           call_usermodehelper_setkeys() adjusts the credentials to sport the
           supplied keyring as the new session keyring.
      
      (11) SELinux.
      
           SELinux has a number of changes, in addition to those to support the LSM
           interface changes mentioned above:
      
           (a) selinux_setprocattr() no longer does its check for whether the
           	 current ptracer can access processes with the new SID inside the lock
           	 that covers getting the ptracer's SID.  Whilst this lock ensures that
           	 the check is done with the ptracer pinned, the result is only valid
           	 until the lock is released, so there's no point doing it inside the
           	 lock.
      
      (12) is_single_threaded().
      
           This function has been extracted from selinux_setprocattr() and put into
           a file of its own in the lib/ directory as join_session_keyring() now
           wants to use it too.
      
           The code in SELinux just checked to see whether a task shared mm_structs
           with other tasks (CLONE_VM), but that isn't good enough.  We really want
           to know if they're part of the same thread group (CLONE_THREAD).
      
      (13) nfsd.
      
           The NFS server daemon now has to use the COW credentials to set the
           credentials it is going to use.  It really needs to pass the credentials
           down to the functions it calls, but it can't do that until other patches
           in this series have been applied.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarJames Morris <jmorris@namei.org>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      d84f4f99
    • David Howells's avatar
      CRED: Pass credentials through dentry_open() · 745ca247
      David Howells authored
      Pass credentials through dentry_open() so that the COW creds patch can have
      SELinux's flush_unauthorized_files() pass the appropriate creds back to itself
      when it opens its null chardev.
      
      The security_dentry_open() call also now takes a creds pointer, as does the
      dentry_open hook in struct security_operations.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarJames Morris <jmorris@namei.org>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      745ca247
    • David Howells's avatar
      CRED: Separate task security context from task_struct · b6dff3ec
      David Howells authored
      Separate the task security context from task_struct.  At this point, the
      security data is temporarily embedded in the task_struct with two pointers
      pointing to it.
      
      Note that the Alpha arch is altered as it refers to (E)UID and (E)GID in
      entry.S via asm-offsets.
      
      With comment fixes Signed-off-by: Marc Dionne <marc.c.dionne@gmail.com>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarJames Morris <jmorris@namei.org>
      Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      b6dff3ec
    • David Howells's avatar
      CRED: Neuter sys_capset() · 1cdcbec1
      David Howells authored
      Take away the ability for sys_capset() to affect processes other than current.
      
      This means that current will not need to lock its own credentials when reading
      them against interference by other processes.
      
      This has effectively been the case for a while anyway, since:
      
       (1) Without LSM enabled, sys_capset() is disallowed.
      
       (2) With file-based capabilities, sys_capset() is neutered.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
      Acked-by: default avatarAndrew G. Morgan <morgan@kernel.org>
      Acked-by: default avatarJames Morris <jmorris@namei.org>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      1cdcbec1
  11. 21 Oct, 2008 1 commit
  12. 13 Oct, 2008 1 commit
  13. 01 Aug, 2008 1 commit
  14. 27 Jul, 2008 9 commits
  15. 24 Jul, 2008 1 commit
  16. 04 Jul, 2008 1 commit
  17. 01 May, 2008 1 commit
  18. 28 Apr, 2008 1 commit
  19. 19 Apr, 2008 3 commits