1. 13 Nov, 2008 3 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
  2. 23 Oct, 2008 1 commit
  3. 19 Apr, 2008 2 commits
  4. 15 Feb, 2008 2 commits
  5. 02 Nov, 2007 1 commit
  6. 22 Oct, 2007 1 commit
  7. 21 May, 2007 1 commit
    • Alexey Dobriyan's avatar
      Detach sched.h from mm.h · e8edc6e0
      Alexey Dobriyan authored
      First thing mm.h does is including sched.h solely for can_do_mlock() inline
      function which has "current" dereference inside. By dealing with can_do_mlock()
      mm.h can be detached from sched.h which is good. See below, why.
      
      This patch
      a) removes unconditional inclusion of sched.h from mm.h
      b) makes can_do_mlock() normal function in mm/mlock.c
      c) exports can_do_mlock() to not break compilation
      d) adds sched.h inclusions back to files that were getting it indirectly.
      e) adds less bloated headers to some files (asm/signal.h, jiffies.h) that were
         getting them indirectly
      
      Net result is:
      a) mm.h users would get less code to open, read, preprocess, parse, ... if
         they don't need sched.h
      b) sched.h stops being dependency for significant number of files:
         on x86_64 allmodconfig touching sched.h results in recompile of 4083 files,
         after patch it's only 3744 (-8.3%).
      
      Cross-compile tested on
      
      	all arm defconfigs, all mips defconfigs, all powerpc defconfigs,
      	alpha alpha-up
      	arm
      	i386 i386-up i386-defconfig i386-allnoconfig
      	ia64 ia64-up
      	m68k
      	mips
      	parisc parisc-up
      	powerpc powerpc-up
      	s390 s390-up
      	sparc sparc-up
      	sparc64 sparc64-up
      	um-x86_64
      	x86_64 x86_64-up x86_64-defconfig x86_64-allnoconfig
      
      as well as my two usual configs.
      Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e8edc6e0
  8. 08 Dec, 2006 1 commit
    • Peter Zijlstra's avatar
      [PATCH] lockdep: annotate nfsd4 recover code · 4b75f78e
      Peter Zijlstra authored
      > =============================================
      > [ INFO: possible recursive locking detected ]
      > 2.6.18-1.2724.lockdepPAE #1
      > ---------------------------------------------
      > nfsd/6884 is trying to acquire lock:
      >  (&inode->i_mutex){--..}, at: [<c04811e5>] vfs_rmdir+0x73/0xf4
      >
      > but task is already holding lock:
      >  (&inode->i_mutex){--..}, at: [<f8dfa621>]
      > nfsd4_clear_clid_dir+0x1f/0x3d [nfsd]
      >
      > other info that might help us debug this:
      > 3 locks held by nfsd/6884:
      >  #0:  (hash_sem){----}, at: [<f8de05eb>] nfsd+0x181/0x2ea [nfsd]
      >  #1:  (client_mutex){--..}, at: [<f8df6d19>]
      > nfsd4_setclientid_confirm+0x3b/0x2cf [nfsd]
      >  #2:  (&inode->i_mutex){--..}, at: [<f8dfa621>]
      > nfsd4_clear_clid_dir+0x1f/0x3d [nfsd]
      >
      > stack backtrace:
      >  [<c040524d>] dump_trace+0x69/0x1af
      >  [<c04053ab>] show_trace_log_lvl+0x18/0x2c
      >  [<c040595f>] show_trace+0xf/0x11
      >  [<c0405a53>] dump_stack+0x15/0x17
      >  [<c043ca7a>] __lock_acquire+0x110/0x9b6
      >  [<c043d91e>] lock_acquire+0x5c/0x7a
      >  [<c061a41b>] __mutex_lock_slowpath+0xde/0x234
      >  [<c04811e5>] vfs_rmdir+0x73/0xf4
      >  [<f8dfa62b>] nfsd4_clear_clid_dir+0x29/0x3d [nfsd]
      >  [<f8dfa733>] nfsd4_remove_clid_dir+0xb8/0xf8 [nfsd]
      >  [<f8df6e90>] nfsd4_setclientid_confirm+0x1b2/0x2cf [nfsd]
      >  [<f8def19a>] nfsd4_proc_compound+0x137a/0x166c [nfsd]
      >  [<f8de00d5>] nfsd_dispatch+0xc5/0x180 [nfsd]
      >  [<f8d09d83>] svc_process+0x3bd/0x631 [sunrpc]
      >  [<f8de0604>] nfsd+0x19a/0x2ea [nfsd]
      >  [<c0404e27>] kernel_thread_helper+0x7/0x10
      > DWARF2 unwinder stuck at kernel_thread_helper+0x7/0x10
      > Leftover inexact backtrace:
      >  =======================
      
      Some nesting annotation to the nfsd4 recovery code.
      The vfs operations called will take dentry->d_inode->i_mutex.
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Neil Brown <neilb@suse.de>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      4b75f78e
  9. 03 Nov, 2006 1 commit
    • Srinivasa Ds's avatar
      [PATCH] NFS4: fix for recursive locking problem · 7ef55b8a
      Srinivasa Ds authored
      When I was performing some operations on NFS, I got below error on server
      side.
      
        =============================================
        [ INFO: possible recursive locking detected ]
        2.6.19-prep #1
        ---------------------------------------------
        nfsd4/3525 is trying to acquire lock:
         (&inode->i_mutex){--..}, at: [<c0611e5a>] mutex_lock+0x21/0x24
      
        but task is already holding lock:
         (&inode->i_mutex){--..}, at: [<c0611e5a>] mutex_lock+0x21/0x24
      
        other info that might help us debug this:
        2 locks held by nfsd4/3525:
         #0:  (client_mutex){--..}, at: [<c0611e5a>] mutex_lock+0x21/0x24
         #1:  (&inode->i_mutex){--..}, at: [<c0611e5a>] mutex_lock+0x21/0x24
      
        stack backtrace:
         [<c04051ed>] show_trace_log_lvl+0x58/0x16a
         [<c04057fa>] show_trace+0xd/0x10
         [<c0405913>] dump_stack+0x19/0x1b
         [<c043b6f1>] __lock_acquire+0x778/0x99c
         [<c043be86>] lock_acquire+0x4b/0x6d
         [<c0611ceb>] __mutex_lock_slowpath+0xbc/0x20a
         [<c0611e5a>] mutex_lock+0x21/0x24
         [<c047fd7e>] vfs_rmdir+0x76/0xf8
         [<f94b7ce9>] nfsd4_clear_clid_dir+0x2c/0x41 [nfsd]
         [<f94b7de9>] nfsd4_remove_clid_dir+0xb1/0xe8 [nfsd]
         [<f94b307b>] laundromat_main+0x9b/0x1c3 [nfsd]
         [<c04333d6>] run_workqueue+0x7a/0xbb
         [<c0433d0b>] worker_thread+0xd2/0x107
         [<c0436285>] kthread+0xc3/0xf2
         [<c0402005>] kernel_thread_helper+0x5/0xb
        ===================================================================
      
      Cause for this problem was,2 successive mutex_lock calls on 2 diffrent inodes ,as shown below
      
      	static int
      	nfsd4_clear_clid_dir(struct dentry *dir, struct dentry *dentry)
      	{
      	        int status;
      
      	        /* For now this directory should already be empty, but we empty it of
              	 * any regular files anyway, just in case the directory was created by
      	         * a kernel from the future.... */
              	nfsd4_list_rec_dir(dentry, nfsd4_remove_clid_file);
      	        mutex_lock(&dir->d_inode->i_mutex);
      	        status = vfs_rmdir(dir->d_inode, dentry);
      	...
      
      	int vfs_rmdir(struct inode *dir, struct dentry *dentry)
      	{
      	        int error = may_delete(dir, dentry, 1);
      
      	        if (error)
      	                return error;
      
      	        if (!dir->i_op || !dir->i_op->rmdir)
              	        return -EPERM;
      
      	        DQUOT_INIT(dir);
      
      	        mutex_lock(&dentry->d_inode->i_mutex);
      	...
      
      So I have developed the patch to overcome this problem.
      Signed-off-by: default avatarSrinivasa DS <srinivasa@in.ibm.com>
      Cc: Neil Brown <neilb@suse.de>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      7ef55b8a
  10. 20 Oct, 2006 1 commit
  11. 03 Oct, 2006 1 commit
    • David Howells's avatar
      [PATCH] VFS: Make filldir_t and struct kstat deal in 64-bit inode numbers · afefdbb2
      David Howells authored
      These patches make the kernel pass 64-bit inode numbers internally when
      communicating to userspace, even on a 32-bit system.  They are required
      because some filesystems have intrinsic 64-bit inode numbers: NFS3+ and XFS
      for example.  The 64-bit inode numbers are then propagated to userspace
      automatically where the arch supports it.
      
      Problems have been seen with userspace (eg: ld.so) using the 64-bit inode
      number returned by stat64() or getdents64() to differentiate files, and
      failing because the 64-bit inode number space was compressed to 32-bits, and
      so overlaps occur.
      
      This patch:
      
      Make filldir_t take a 64-bit inode number and struct kstat carry a 64-bit
      inode number so that 64-bit inode numbers can be passed back to userspace.
      
      The stat functions then returns the full 64-bit inode number where
      available and where possible.  If it is not possible to represent the inode
      number supplied by the filesystem in the field provided by userspace, then
      error EOVERFLOW will be issued.
      
      Similarly, the getdents/readdir functions now pass the full 64-bit inode
      number to userspace where possible, returning EOVERFLOW instead when a
      directory entry is encountered that can't be properly represented.
      
      Note that this means that some inodes will not be stat'able on a 32-bit
      system with old libraries where they were before - but it does mean that
      there will be no ambiguity over what a 32-bit inode number refers to.
      
      Note similarly that directory scans may be cut short with an error on a
      32-bit system with old libraries where the scan would work before for the
      same reasons.
      
      It is judged unlikely that this situation will occur because modern glibc
      uses 64-bit capable versions of stat and getdents class functions
      exclusively, and that older systems are unlikely to encounter
      unrepresentable inode numbers anyway.
      
      [akpm: alpha build fix]
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      afefdbb2
  12. 21 Sep, 2006 1 commit
  13. 19 Jan, 2006 2 commits
  14. 09 Jan, 2006 1 commit
  15. 02 Sep, 2005 2 commits
  16. 08 Jul, 2005 3 commits
  17. 24 Jun, 2005 4 commits