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* include cleanup: Update gfp.h and slab.h includes to prepare for breaking ↵Tejun Heo2010-03-301-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
* seq_file: constify seq_operationsJames Morris2009-09-231-3/+3
| | | | | | | | | | | | | | Make all seq_operations structs const, to help mitigate against revectoring user-triggerable function pointers. This is derived from the grsecurity patch, although generated from scratch because it's simpler than extracting the changes from there. Signed-off-by: James Morris <jmorris@namei.org> Acked-by: Serge Hallyn <serue@us.ibm.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'for-linus' of ↵Linus Torvalds2009-06-111-1/+67
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6 * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6: (44 commits) nommu: Provide mmap_min_addr definition. TOMOYO: Add description of lists and structures. TOMOYO: Remove unused field. integrity: ima audit dentry_open failure TOMOYO: Remove unused parameter. security: use mmap_min_addr indepedently of security models TOMOYO: Simplify policy reader. TOMOYO: Remove redundant markers. SELinux: define audit permissions for audit tree netlink messages TOMOYO: Remove unused mutex. tomoyo: avoid get+put of task_struct smack: Remove redundant initialization. integrity: nfsd imbalance bug fix rootplug: Remove redundant initialization. smack: do not beyond ARRAY_SIZE of data integrity: move ima_counts_get integrity: path_check update IMA: Add __init notation to ima functions IMA: Minimal IMA policy and boot param for TCB IMA policy selinux: remove obsolete read buffer limit from sel_read_bool ...
| * smack: do not beyond ARRAY_SIZE of dataRoel Kluin2009-05-221-1/+1
| | | | | | | | | | | | | | | | Do not go beyond ARRAY_SIZE of data Signed-off-by: Roel Kluin <roel.kluin@gmail.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: James Morris <jmorris@namei.org>
| * smack: implement logging V3Etienne Basset2009-04-141-0/+66
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | the following patch, add logging of Smack security decisions. This is of course very useful to understand what your current smack policy does. As suggested by Casey, it also now forbids labels with ', " or \ It introduces a '/smack/logging' switch : 0: no logging 1: log denied (default) 2: log accepted 3: log denied&accepted Signed-off-by: Etienne Basset <etienne.basset@numericable.fr> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Acked-by: Eric Paris <eparis@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
* | rculist: use list_entry_rcu in places where it's appropriateJiri Pirko2009-04-151-4/+4
|/ | | | | | | | | | | Use previously introduced list_entry_rcu instead of an open-coded list_entry + rcu_dereference combination. Signed-off-by: Jiri Pirko <jpirko@redhat.com> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: dipankar@in.ibm.com LKML-Reference: <20090414181715.GA3634@psychotron.englab.brq.redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* smack: Add a new '-CIPSO' option to the network address label configurationEtienne Basset2009-03-281-8/+30
| | | | | | | | | | | | | This patch adds a new special option '-CIPSO' to the Smack subsystem. When used in the netlabel list, it means "use CIPSO networking". A use case is when your local network speaks CIPSO and you want also to connect to the unlabeled Internet. This patch also add some documentation describing that. The patch also corrects an oops when setting a '' SMACK64 xattr to a file. Signed-off-by: Etienne Basset <etienne.basset@numericable.fr> Signed-off-by: Paul Moore <paul.moore@hp.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: James Morris <jmorris@namei.org>
* smack: convert smack to standard linux listsEtienne Basset2009-03-261-79/+101
| | | | | | | | | | | the following patch (on top of 2.6.29) converts Smack lists to standard linux lists Please review and consider for inclusion in 2.6.30-rc regards, Etienne Signed-off-by: Etienne Basset <etienne.basset@numericable.fr> Acked-by: Casey Schaufler <casey@schaufler-ca.com>
* smack: fixes for unlabeled host supportetienne2009-03-051-15/+49
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The following patch (against 2.6.29rc5) fixes a few issues in the smack/netlabel "unlabeled host support" functionnality that was added in 2.6.29rc. It should go in before -final. 1) smack_host_label disregard a "0.0.0.0/0 @" rule (or other label), preventing 'tagged' tasks to access Internet (many systems drop packets with IP options) 2) netmasks were not handled correctly, they were stored in a way _not equivalent_ to conversion to be32 (it was equivalent for /0, /8, /16, /24, /32 masks but not other masks) 3) smack_netlbladdr prefixes (IP/mask) were not consistent (mask&IP was not done), so there could have been different list entries for the same IP prefix; if those entries had different labels, well ... 4) they were not sorted 1) 2) 3) are bugs, 4) is a more cosmetic issue. The patch : -creates a new helper smk_netlbladdr_insert to insert a smk_netlbladdr, -sorted by netmask length -use the new sorted nature of smack_netlbladdrs list to simplify smack_host_label : the first match _will_ be the more specific -corrects endianness issues in smk_write_netlbladdr & netlbladdr_seq_show Signed-off-by: <etienne.basset@numericable.fr> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Reviewed-by: Paul Moore <paul.moore@hp.com> Signed-off-by: James Morris <jmorris@namei.org>
* smack: fix lots of kernel-doc notationRandy Dunlap2009-02-191-7/+8
| | | | | | | | Fix/add kernel-doc notation and fix typos in security/smack/. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: James Morris <jmorris@namei.org>
* smackfs load append mode fixCasey Schaufler2009-01-271-1/+1
| | | | | | | | | | | Given just how hard it is to find the code that uses MAY_APPEND it's probably not a big surprise that this went unnoticed for so long. The Smack rules loading code is incorrectly setting the MAY_READ bit when MAY_APPEND is requested. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> Reviewed-by: James Morris <jmorris@namei.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* remove lots of double-semicolonsFernando Carrijo2009-01-081-1/+1
| | | | | | | | | | | | | Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Acked-by: Theodore Ts'o <tytso@mit.edu> Acked-by: Mark Fasheh <mfasheh@suse.com> Acked-by: David S. Miller <davem@davemloft.net> Cc: James Morris <jmorris@namei.org> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Acked-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* smack: Add support for unlabeled network hosts and networksCasey Schaufler2008-12-311-129/+235
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add support for unlabeled network hosts and networks. Relies heavily on Paul Moore's netlabel support. Creates a new entry in /smack called netlabel. Writes to /smack/netlabel take the form: A.B.C.D LABEL or A.B.C.D/N LABEL where A.B.C.D is a network address, N is an integer between 0-32, and LABEL is the Smack label to be used. If /N is omitted /32 is assumed. N designates the netmask for the address. Entries are matched by the most specific address/mask pair. 0.0.0.0/0 will match everything, while 192.168.1.117/32 will match exactly one host. A new system label "@", pronounced "web", is defined. Processes can not be assigned the web label. An address assigned the web label can be written to by any process, and packets coming from a web address can be written to any socket. Use of the web label is a violation of any strict MAC policy, but the web label has been requested many times. The nltype entry has been removed from /smack. It did not work right and the netlabel interface can be used to specify that all hosts be treated as unlabeled. CIPSO labels on incoming packets will be honored, even from designated single label hosts. Single label hosts can only be written to by processes with labels that can write to the label of the host. Packets sent to single label hosts will always be unlabeled. Once added a single label designation cannot be removed, however the label may be changed. The behavior of the ambient label remains unchanged. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Paul Moore <paul.moore@hp.com>
* netlabel: Update kernel configuration APIPaul Moore2008-12-311-5/+16
| | | | | | | | Update the NetLabel kernel API to expose the new features added in kernel releases 2.6.25 and 2.6.28: the static/fallback label functionality and network address based selectors. Signed-off-by: Paul Moore <paul.moore@hp.com>
* smackfs: check for allocation failures in smk_set_access()Sergio Luis2008-12-251-4/+16
| | | | | | | | | | | | | | | | | | | | smackfs: check for allocation failures in smk_set_access() While adding a new subject/object pair to smack_list, smk_set_access() didn't check the return of kzalloc(). This patch changes smk_set_access() to return 0 or -ENOMEM, based on kzalloc()'s return. It also updates its caller, smk_write_load(), to check for smk_set_access()'s return, given it is no longer a void return function. Signed-off-by: Sergio Luis <sergio@larces.uece.br> To: Casey Schaufler <casey@schaufler-ca.com> Cc: Ahmed S. Darwish <darwish.07@gmail.com> Cc: LSM <linux-security-module@vger.kernel.org> Cc: LKLM <linux-kernel@vger.kernel.org> Acked-by: Casey Schaufler <casey@schaufler-ca.com>
* CRED: Wrap current->cred and a few other accessorsDavid Howells2008-11-141-2/+2
| | | | | | | | | | Wrap current->cred and a few other accessors to hide their actual implementation. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Acked-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
* CRED: Separate task security context from task_structDavid Howells2008-11-141-3/+3
| | | | | | | | | | | | | | | | 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: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Acked-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
* Merge branch 'master' of ↵James Morris2008-10-111-1/+3
|\ | | | | | | git://git.infradead.org/users/pcmoore/lblnet-2.6_next into next
| * netlabel: Replace protocol/NetLabel linking with refrerence countsPaul Moore2008-10-101-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | NetLabel has always had a list of backpointers in the CIPSO DOI definition structure which pointed to the NetLabel LSM domain mapping structures which referenced the CIPSO DOI struct. The rationale for this was that when an administrator removed a CIPSO DOI from the system all of the associated NetLabel LSM domain mappings should be removed as well; a list of backpointers made this a simple operation. Unfortunately, while the backpointers did make the removal easier they were a bit of a mess from an implementation point of view which was making further development difficult. Since the removal of a CIPSO DOI is a realtively rare event it seems to make sense to remove this backpointer list as the optimization was hurting us more then it was helping. However, we still need to be able to track when a CIPSO DOI definition is being used so replace the backpointer list with a reference count. In order to preserve the current functionality of removing the associated LSM domain mappings when a CIPSO DOI is removed we walk the LSM domain mapping table, removing the relevant entries. Signed-off-by: Paul Moore <paul.moore@hp.com> Reviewed-by: James Morris <jmorris@namei.org>
* | smack: limit privilege by labelCasey Schaufler2008-08-051-0/+92
|/ | | | | | | | | | | | | | | | | | | | | | | | | | There have been a number of requests to make the Smack LSM enforce MAC even in the face of privilege, either capability based or superuser based. This is not universally desired, however, so it seems desirable to make it optional. Further, at least one legacy OS implemented a scheme whereby only processes running with one particular label could be exempt from MAC. This patch supports these three cases. If /smack/onlycap is empty (unset or null-string) privilege is enforced in the normal way. If /smack/onlycap contains a label only processes running with that label may be MAC exempt. If the label in /smack/onlycap is the star label ("*") the semantics of the star label combine with the privilege restrictions to prevent any violations of MAC, even in the presence of privilege. Again, this will be independent of the privilege scheme. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> Reviewed-by: James Morris <jmorris@namei.org>
* Merge branch 'audit.b50' of ↵Linus Torvalds2008-04-291-0/+2
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current * 'audit.b50' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current: [PATCH] new predicate - AUDIT_FILETYPE [patch 2/2] Use find_task_by_vpid in audit code [patch 1/2] audit: let userspace fully control TTY input auditing [PATCH 2/2] audit: fix sparse shadowed variable warnings [PATCH 1/2] audit: move extern declarations to audit.h Audit: MAINTAINERS update Audit: increase the maximum length of the key field Audit: standardize string audit interfaces Audit: stop deadlock from signals under load Audit: save audit_backlog_limit audit messages in case auditd comes back Audit: collect sessionid in netlink messages Audit: end printk with newline
| * Audit: collect sessionid in netlink messagesEric Paris2008-04-281-0/+2
| | | | | | | | | | | | | | | | | | | | Previously I added sessionid output to all audit messages where it was available but we still didn't know the sessionid of the sender of netlink messages. This patch adds that information to netlink messages so we can audit who sent netlink messages. Signed-off-by: Eric Paris <eparis@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* | smack: make smk_cipso_doi() and smk_unlbl_ambient()Casey Schaufler2008-04-281-2/+2
|/ | | | | | | | | The functions smk_cipso_doi and smk_unlbl_ambient are not used outside smackfs.c and should hence be static. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Security: Introduce security= boot parameterAhmed S. Darwish2008-04-191-1/+10
| | | | | | | | | | | | | | | | | | | | | Add the security= boot parameter. This is done to avoid LSM registration clashes in case of more than one bult-in module. User can choose a security module to enable at boot. If no security= boot parameter is specified, only the first LSM asking for registration will be loaded. An invalid security module name will be treated as if no module has been chosen. LSM modules must check now if they are allowed to register by calling security_module_enable(ops) first. Modify SELinux and SMACK to do so. Do not let SMACK register smackfs if it was not chosen on boot. Smackfs assumes that smack hooks are registered and the initial task security setup (swapper->security) is done. Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com> Acked-by: James Morris <jmorris@namei.org>
* smackfs: remove redundant lock, fix open(,O_RDWR)Ahmed S. Darwish2008-03-241-33/+2
| | | | | | | | | | | | | | | | Older smackfs was parsing MAC rules by characters, thus a need of locking write sessions on open() was needed. This lock is no longer useful now since each rule is handled by a single write() call. This is also a bugfix since seq_open() was not called if an open() O_RDWR flag was given, leading to a seq_read() without an initialized seq_file, thus an Oops. Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com> Reported-by: Jonathan Corbet <corbet@lwn.net> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* smackfs: do not trust `count' in inodes write()sAhmed S. Darwish2008-03-131-11/+20
| | | | | | | | | | | | | | | | Smackfs write() implementation does not put a higher bound on the number of bytes to copy from user-space. This may lead to a DOS attack if a malicious `count' field is given. Assure that given `count' is exactly the length needed for a /smack/load rule. In case of /smack/cipso where the length is relative, assure that `count' does not exceed the size needed for a buffer representing maximum possible number of CIPSO 2.2 categories. Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Smack: unlabeled outgoing ambient packetsCasey Schaufler2008-02-191-15/+46
| | | | | | | | | | | | | | | | | | | | | Smack uses CIPSO labeling, but allows for unlabeled packets by specifying an "ambient" label that is applied to incoming unlabeled packets. Because the other end of the connection may dislike IP options, and ssh is one know application that behaves thus, it is prudent to respond in kind. This patch changes the network labeling behavior such that an outgoing packet that would be given a CIPSO label that matches the ambient label is left unlabeled. An "unlbl" domain is added and the netlabel defaulting mechanism invoked rather than assuming that everything is CIPSO. Locking has been added around changes to the ambient label as the mechanisms used to do so are more involved. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> Acked-by: Paul Moore <paul.moore@hp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Smack: Simplified Mandatory Access Control KernelCasey Schaufler2008-02-051-0/+981
Smack is the Simplified Mandatory Access Control Kernel. Smack implements mandatory access control (MAC) using labels attached to tasks and data containers, including files, SVIPC, and other tasks. Smack is a kernel based scheme that requires an absolute minimum of application support and a very small amount of configuration data. Smack uses extended attributes and provides a set of general mount options, borrowing technics used elsewhere. Smack uses netlabel for CIPSO labeling. Smack provides a pseudo-filesystem smackfs that is used for manipulation of system Smack attributes. The patch, patches for ls and sshd, a README, a startup script, and x86 binaries for ls and sshd are also available on http://www.schaufler-ca.com Development has been done using Fedora Core 7 in a virtual machine environment and on an old Sony laptop. Smack provides mandatory access controls based on the label attached to a task and the label attached to the object it is attempting to access. Smack labels are deliberately short (1-23 characters) text strings. Single character labels using special characters are reserved for system use. The only operation applied to Smack labels is equality comparison. No wildcards or expressions, regular or otherwise, are used. Smack labels are composed of printable characters and may not include "/". A file always gets the Smack label of the task that created it. Smack defines and uses these labels: "*" - pronounced "star" "_" - pronounced "floor" "^" - pronounced "hat" "?" - pronounced "huh" The access rules enforced by Smack are, in order: 1. Any access requested by a task labeled "*" is denied. 2. A read or execute access requested by a task labeled "^" is permitted. 3. A read or execute access requested on an object labeled "_" is permitted. 4. Any access requested on an object labeled "*" is permitted. 5. Any access requested by a task on an object with the same label is permitted. 6. Any access requested that is explicitly defined in the loaded rule set is permitted. 7. Any other access is denied. Rules may be explicitly defined by writing subject,object,access triples to /smack/load. Smack rule sets can be easily defined that describe Bell&LaPadula sensitivity, Biba integrity, and a variety of interesting configurations. Smack rule sets can be modified on the fly to accommodate changes in the operating environment or even the time of day. Some practical use cases: Hierarchical levels. The less common of the two usual uses for MLS systems is to define hierarchical levels, often unclassified, confidential, secret, and so on. To set up smack to support this, these rules could be defined: C Unclass rx S C rx S Unclass rx TS S rx TS C rx TS Unclass rx A TS process can read S, C, and Unclass data, but cannot write it. An S process can read C and Unclass. Note that specifying that TS can read S and S can read C does not imply TS can read C, it has to be explicitly stated. Non-hierarchical categories. This is the more common of the usual uses for an MLS system. Since the default rule is that a subject cannot access an object with a different label no access rules are required to implement compartmentalization. A case that the Bell & LaPadula policy does not allow is demonstrated with this Smack access rule: A case that Bell&LaPadula does not allow that Smack does: ESPN ABC r ABC ESPN r On my portable video device I have two applications, one that shows ABC programming and the other ESPN programming. ESPN wants to show me sport stories that show up as news, and ABC will only provide minimal information about a sports story if ESPN is covering it. Each side can look at the other's info, neither can change the other. Neither can see what FOX is up to, which is just as well all things considered. Another case that I especially like: SatData Guard w Guard Publish w A program running with the Guard label opens a UDP socket and accepts messages sent by a program running with a SatData label. The Guard program inspects the message to ensure it is wholesome and if it is sends it to a program running with the Publish label. This program then puts the information passed in an appropriate place. Note that the Guard program cannot write to a Publish file system object because file system semanitic require read as well as write. The four cases (categories, levels, mutual read, guardbox) here are all quite real, and problems I've been asked to solve over the years. The first two are easy to do with traditonal MLS systems while the last two you can't without invoking privilege, at least for a while. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> Cc: Joshua Brindle <method@manicmethod.com> Cc: Paul Moore <paul.moore@hp.com> Cc: Stephen Smalley <sds@tycho.nsa.gov> Cc: Chris Wright <chrisw@sous-sol.org> Cc: James Morris <jmorris@namei.org> Cc: "Ahmed S. Darwish" <darwish.07@gmail.com> Cc: Andrew G. Morgan <morgan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>