guarantee atomicity of the operation for other semaphore consumers.
In particular, this should guard against access to the semaphore with
not done or partially done MAC label assignment.
Reviewed by: rwatson
MFC after: 1 month
on SysV semaphores.
The squeeze of the semaphore array in the kern_semctl() modifies
sem_base for the semaphores with sem_base greater then sem_base of
the removed semaphore, as well as the values of the semaphores,
without locking their mutex. This can lead to (killable) hangs or
unexpected behaviour of the processes performing any sem operations
while other process does IPC_RMID.
The semexit_myhook() eventhandler unlocks SEMUNDO_LOCK() while
accessing *suptr. This allows for IPC_RMID for the sem id to be
performed in parallel with undo hook referenced by the current undo
structure. This leads to the panic("semexit - semid not allocated") [1].
The semaphore creation is protected by Giant, while IPC_RMID is done
while only semaphore mutex is held. This seems to result in invalid
values for semtot, causing random ENOSPC error returns [2].
Redo the locking of the semaphores lifetime cycle. Delegate the
sem_mtx to the sole purpose of protecting semget() and
semctl(IPC_RMID). Introduce new sem_undo_mtx to protect SEM_UNDO
handling. Remove the Giant remnants from the code.
Note that mac_sysvsem_check_semget() and mac_sysvsem_create() are
now called while sem_mtx is held, as well as mac_sysvsem_cleanup() [3].
When semaphore is removed, acquire semaphore locks for all semaphores
with sem_base that is going to be changed by squeeze of the sema
array. The lock order is not important there, because the region is
protected by sem_mtx.
Organize both used and free sem_undo structures into the lists,
protected by sem_undo_mtx. In semexit_myhook(), remove sem_undo
structure that is being processed, from used list, without putting it
onto the free to prevent modifications by other threads. This allows
for sem_undo_lock to be dropped to acquire individial semaphore locks
without violating lock order. Since IPC_RMID may no longer find this
sem_undo, do tolerate references to unallocated semaphores in undo
structure, and check sequential number to not undo unrelated semaphore
with the same id.
While there, convert functions definitions to ANSI C and fix small
style(9) glitches.
Reported by: Omer Faruk Sen <omerfsen gmail com> [1], pho [2]
Reviewed by: rwatson [3]
Tested by: pho
MFC after: 1 month
from Mac OS X Leopard--rationalize naming for entry points to
the following general forms:
mac_<object>_<method/action>
mac_<object>_check_<method/action>
The previous naming scheme was inconsistent and mostly
reversed from the new scheme. Also, make object types more
consistent and remove spaces from object types that contain
multiple parts ("posix_sem" -> "posixsem") to make mechanical
parsing easier. Introduce a new "netinet" object type for
certain IPv4/IPv6-related methods. Also simplify, slightly,
some entry point names.
All MAC policy modules will need to be recompiled, and modules
not updates as part of this commit will need to be modified to
conform to the new KPI.
Sponsored by: SPARTA (original patches against Mac OS X)
Obtained from: TrustedBSD Project, Apple Computer
- Remove also "MP SAFE" after prior "MPSAFE" pass. (suggested by bde)
- Remove extra blank lines in some cases.
- Add extra blank lines in some cases.
- Remove no-op comments consisting solely of the function name, the word
"syscall", or the system call name.
- Add punctuation.
- Re-wrap some comments.
system calls now enter without Giant held, and then in some cases, acquire
Giant explicitly.
Remove a number of other MPSAFE annotations in the credential code and
tweak one or two other adjacent comments.
begun with a repo-copy of mac.h to mac_framework.h. sys/mac.h now
contains the userspace and user<->kernel API and definitions, with all
in-kernel interfaces moved to mac_framework.h, which is now included
across most of the kernel instead.
This change is the first step in a larger cleanup and sweep of MAC
Framework interfaces in the kernel, and will not be MFC'd.
Obtained from: TrustedBSD Project
Sponsored by: SPARTA
appears to be serving a useful purpose, as it was used during initial
development of MAC support for System V IPC.
MFC after: 1 month
Obtained from: TrustedBSD Project
Suggested by: Christopher dot Vance at SPARTA dot com
mostly consists of pushing a few copyin's and copyout's up into
__semctl() as all the other callers were already doing the UIO_SYSSPACE
case. This also changes kern_semctl() to set the return value in a passed
in pointer to a register_t rather than td->td_retval[0] directly so that
callers can only set td->td_retval[0] if all the various copyout's succeed.
As a result of these changes, kern_semctl() no longer does copyin/copyout
(except for GETALL/SETALL) so simplify the locking to acquire the semakptr
mutex before the MAC check and hold it all the way until the end of the
big switch statement. The GETALL/SETALL cases have to temporarily drop it
while they do copyin/malloc and copyout. Also, simplify the SETALL case to
remove handling for a non-existent race condition.
a local 'semid' variable which was the array index and used uap->semid
as the original IPC id. During the kern_semctl() conversion those two
variables were collapsed into a single 'semid' variable breaking the
places that needed the original IPC ID. To fix, add a new 'semidx'
variable to hold the array index and leave 'semid' unmolested as the IPC
id. While I'm here, explicitly document that the (undocumented, at least
in semctl(2)) SEM_STAT command curiously expects an array index in the
'semid' parameter rather than an IPC id.
Submitted by: maxim
to a copied-in copy of the 'union semun' and a uioseg to indicate which
memory space the 'buf' pointer of the union points to. This is then used
in linux_semctl() and svr4_sys_semctl() to eliminate use of the stackgap.
- Mark linux_ipc() and svr4_sys_semsys() MPSAFE.
- Move sonewconn(), which creates new sockets for incoming connections on
listen sockets, so that all socket allocate code is together in
uipc_socket.c.
- Move 'maxsockets' and associated sysctls to uipc_socket.c with the
socket allocation code.
- Move kern.ipc sysctl node to uipc_socket.c, add a SYSCTL_DECL() for it
to sysctl.h and remove lots of scattered implementations in various
IPC modules.
- Sort sodealloc() after soalloc() in uipc_socket.c for dependency order
reasons. Statisticize soalloc() and sodealloc() as they are now
required only in uipc_socket.c, and are internal to the socket
implementation.
After this change, socket allocation and deallocation is entirely
centralized in one file, and uipc_socket2.c consists entirely of socket
buffer manipulation and default protocol switch functions.
MFC after: 1 month
points to convert _sema() to _sem() for consistency purposes with
respect to the other semaphore-related entry points:
mac_init_sysv_sema() -> mac_init_sysv_sem()
mac_destroy_sysv_sem() -> mac_destroy_sysv_sem()
mac_create_sysv_sema() -> mac_create_sysv_sem()
mac_cleanup_sysv_sema() -> mac_cleanup_sysv_sem()
Congruent changes are made to the policy interface to support this.
Obtained from: TrustedBSD Project
Sponsored by: SPAWAR, SPARTA
This information will be very useful for people who are tuning applications
which have a dependence on IPC mechanisms.
The following OIDs were documented:
Message queues:
kern.ipc.msgmax
kern.ipc.msgmni
kern.ipc.msgmnb
kern.ipc.msgtlq
kern.ipc.msgssz
kern.ipc.msgseg
Semaphores:
kern.ipc.semmap
kern.ipc.semmni
kern.ipc.semmns
kern.ipc.semmnu
kern.ipc.semmsl
kern.ipc.semopm
kern.ipc.semume
kern.ipc.semusz
kern.ipc.semvmx
kern.ipc.semaem
Shared memory:
kern.ipc.shmmax
kern.ipc.shmmin
kern.ipc.shmmni
kern.ipc.shmseg
kern.ipc.shmall
kern.ipc.shm_use_phys
kern.ipc.shm_allow_removed
kern.ipc.shmsegs
These new descriptions can be viewed using sysctl -d
PR: kern/65219
Submitted by: Dan Nelson <dnelson at allantgroup dot com> (modified)
No objections: developers@
Descriptions reviewed by: gnn
MFC after: 1 week
return EINVAL rather than setting error, and don't free sops
unconditionally. The first change was merged accidentally as part of
the larger set of changes to introduce MAC labels and access control,
and potentially lead to continued processing of a request even after
it was determined to be invalid. The second change was due to changes
in the semaphore code since the original work was performed.
Pointed out by: truckman
to be modified and extended without breaking the user space ABI:
Use _kernel variants on _ds structures for System V sempahores, message
queues, and shared memory. When interfacing with userspace, export
only the _ds subsets of the _kernel data structures. A lot of search
and replace.
Define the message structure in the _KERNEL portion of msg.h so that it
can be used by other kernel consumers, but not exposed to user space.
Submitted by: Dandekar Hrishikesh <rishi_dandekar at sbcglobal dot net>
Obtained from: TrustedBSD Project
Sponsored by: DARPA, SPAWAR, McAfee Research
free one sem_undo with un_cnt == 0 instead of all of them. This is a
temporary workaround until the SLIST_FOREACH_PREVPTR loop gets fixed so
that it doesn't cause cycles in semu_list when removing multiple adjacent
items. It might be easier to just use (doubly-linked) LISTs here instead
of complicated SLIST code to achieve O(1) removals.
This bug manifested itself as a complete lockup under heavy semaphore use
by multiple processes with the SEM_UNDO flag set.
PR: 58984
flexible process_fork, process_exec, and process_exit eventhandlers. This
reduces code duplication and also means that I don't have to go duplicate
the eventhandler locking three more times for each of at_fork, at_exec, and
at_exit.
Reviewed by: phk, jake, almost complete silence on arch@
there is a global lock over the undo structures because of the way
they are managed.
Switch to using SLIST instead of rolling our own linked list.
Fix several races where a permission check was done before a
copyin/copyout, if the copy happened to fault it may have been
possible to race for access to a semaphore set that one shouldn't
have access to.
Requested by: rwatson
Tested by: NetBSD regression suite.
- Move jail checks and some other checks involving constants and stack
variables out from under Giant. This isn't perfectly safe atm because
jail_sysvipc_allowed is read w/o a lock meaning that its value could be
stale. This global variable will soon become a per-jail flag, however,
at which time it will either not need a lock or will use the prison lock.
