diff options
Diffstat (limited to 'ipc')
| -rw-r--r-- | ipc/ipc_sysctl.c | 20 | ||||
| -rw-r--r-- | ipc/msg.c | 13 | ||||
| -rw-r--r-- | ipc/sem.c | 222 | ||||
| -rw-r--r-- | ipc/util.c | 27 |
4 files changed, 198 insertions, 84 deletions
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c index 130dfece27a..b0e99deb6d0 100644 --- a/ipc/ipc_sysctl.c +++ b/ipc/ipc_sysctl.c @@ -62,7 +62,7 @@ static int proc_ipc_dointvec_minmax_orphans(ctl_table *table, int write, return err; } -static int proc_ipc_callback_dointvec(ctl_table *table, int write, +static int proc_ipc_callback_dointvec_minmax(ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table ipc_table; @@ -72,7 +72,7 @@ static int proc_ipc_callback_dointvec(ctl_table *table, int write, memcpy(&ipc_table, table, sizeof(ipc_table)); ipc_table.data = get_ipc(table); - rc = proc_dointvec(&ipc_table, write, buffer, lenp, ppos); + rc = proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos); if (write && !rc && lenp_bef == *lenp) /* @@ -152,15 +152,13 @@ static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write, #define proc_ipc_dointvec NULL #define proc_ipc_dointvec_minmax NULL #define proc_ipc_dointvec_minmax_orphans NULL -#define proc_ipc_callback_dointvec NULL +#define proc_ipc_callback_dointvec_minmax NULL #define proc_ipcauto_dointvec_minmax NULL #endif static int zero; static int one = 1; -#ifdef CONFIG_CHECKPOINT_RESTORE static int int_max = INT_MAX; -#endif static struct ctl_table ipc_kern_table[] = { { @@ -198,21 +196,27 @@ static struct ctl_table ipc_kern_table[] = { .data = &init_ipc_ns.msg_ctlmax, .maxlen = sizeof (init_ipc_ns.msg_ctlmax), .mode = 0644, - .proc_handler = proc_ipc_dointvec, + .proc_handler = proc_ipc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &int_max, }, { .procname = "msgmni", .data = &init_ipc_ns.msg_ctlmni, .maxlen = sizeof (init_ipc_ns.msg_ctlmni), .mode = 0644, - .proc_handler = proc_ipc_callback_dointvec, + .proc_handler = proc_ipc_callback_dointvec_minmax, + .extra1 = &zero, + .extra2 = &int_max, }, { .procname = "msgmnb", .data = &init_ipc_ns.msg_ctlmnb, .maxlen = sizeof (init_ipc_ns.msg_ctlmnb), .mode = 0644, - .proc_handler = proc_ipc_dointvec, + .proc_handler = proc_ipc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &int_max, }, { .procname = "sem", diff --git a/ipc/msg.c b/ipc/msg.c index 9e4310c546a..558aa91186b 100644 --- a/ipc/msg.c +++ b/ipc/msg.c @@ -695,6 +695,12 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext, if (ipcperms(ns, &msq->q_perm, S_IWUGO)) goto out_unlock0; + /* raced with RMID? */ + if (msq->q_perm.deleted) { + err = -EIDRM; + goto out_unlock0; + } + err = security_msg_queue_msgsnd(msq, msg, msgflg); if (err) goto out_unlock0; @@ -901,6 +907,13 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl goto out_unlock1; ipc_lock_object(&msq->q_perm); + + /* raced with RMID? */ + if (msq->q_perm.deleted) { + msg = ERR_PTR(-EIDRM); + goto out_unlock0; + } + msg = find_msg(msq, &msgtyp, mode); if (!IS_ERR(msg)) { /* diff --git a/ipc/sem.c b/ipc/sem.c index 19c8b980d1f..db9d241af13 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -253,70 +253,112 @@ static void sem_rcu_free(struct rcu_head *head) } /* + * Wait until all currently ongoing simple ops have completed. + * Caller must own sem_perm.lock. + * New simple ops cannot start, because simple ops first check + * that sem_perm.lock is free. + * that a) sem_perm.lock is free and b) complex_count is 0. + */ +static void sem_wait_array(struct sem_array *sma) +{ + int i; + struct sem *sem; + + if (sma->complex_count) { + /* The thread that increased sma->complex_count waited on + * all sem->lock locks. Thus we don't need to wait again. + */ + return; + } + + for (i = 0; i < sma->sem_nsems; i++) { + sem = sma->sem_base + i; + spin_unlock_wait(&sem->lock); + } +} + +/* * If the request contains only one semaphore operation, and there are * no complex transactions pending, lock only the semaphore involved. * Otherwise, lock the entire semaphore array, since we either have * multiple semaphores in our own semops, or we need to look at * semaphores from other pending complex operations. - * - * Carefully guard against sma->complex_count changing between zero - * and non-zero while we are spinning for the lock. The value of - * sma->complex_count cannot change while we are holding the lock, - * so sem_unlock should be fine. - * - * The global lock path checks that all the local locks have been released, - * checking each local lock once. This means that the local lock paths - * cannot start their critical sections while the global lock is held. */ static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, int nsops) { - int locknum; - again: - if (nsops == 1 && !sma->complex_count) { - struct sem *sem = sma->sem_base + sops->sem_num; + struct sem *sem; - /* Lock just the semaphore we are interested in. */ - spin_lock(&sem->lock); + if (nsops != 1) { + /* Complex operation - acquire a full lock */ + ipc_lock_object(&sma->sem_perm); - /* - * If sma->complex_count was set while we were spinning, - * we may need to look at things we did not lock here. + /* And wait until all simple ops that are processed + * right now have dropped their locks. */ - if (unlikely(sma->complex_count)) { - spin_unlock(&sem->lock); - goto lock_array; - } + sem_wait_array(sma); + return -1; + } + + /* + * Only one semaphore affected - try to optimize locking. + * The rules are: + * - optimized locking is possible if no complex operation + * is either enqueued or processed right now. + * - The test for enqueued complex ops is simple: + * sma->complex_count != 0 + * - Testing for complex ops that are processed right now is + * a bit more difficult. Complex ops acquire the full lock + * and first wait that the running simple ops have completed. + * (see above) + * Thus: If we own a simple lock and the global lock is free + * and complex_count is now 0, then it will stay 0 and + * thus just locking sem->lock is sufficient. + */ + sem = sma->sem_base + sops->sem_num; + if (sma->complex_count == 0) { /* - * Another process is holding the global lock on the - * sem_array; we cannot enter our critical section, - * but have to wait for the global lock to be released. + * It appears that no complex operation is around. + * Acquire the per-semaphore lock. */ - if (unlikely(spin_is_locked(&sma->sem_perm.lock))) { - spin_unlock(&sem->lock); - spin_unlock_wait(&sma->sem_perm.lock); - goto again; + spin_lock(&sem->lock); + + /* Then check that the global lock is free */ + if (!spin_is_locked(&sma->sem_perm.lock)) { + /* spin_is_locked() is not a memory barrier */ + smp_mb(); + + /* Now repeat the test of complex_count: + * It can't change anymore until we drop sem->lock. + * Thus: if is now 0, then it will stay 0. + */ + if (sma->complex_count == 0) { + /* fast path successful! */ + return sops->sem_num; + } } + spin_unlock(&sem->lock); + } + + /* slow path: acquire the full lock */ + ipc_lock_object(&sma->sem_perm); - locknum = sops->sem_num; + if (sma->complex_count == 0) { + /* False alarm: + * There is no complex operation, thus we can switch + * back to the fast path. + */ + spin_lock(&sem->lock); + ipc_unlock_object(&sma->sem_perm); + return sops->sem_num; } else { - int i; - /* - * Lock the semaphore array, and wait for all of the - * individual semaphore locks to go away. The code - * above ensures no new single-lock holders will enter - * their critical section while the array lock is held. + /* Not a false alarm, thus complete the sequence for a + * full lock. */ - lock_array: - ipc_lock_object(&sma->sem_perm); - for (i = 0; i < sma->sem_nsems; i++) { - struct sem *sem = sma->sem_base + i; - spin_unlock_wait(&sem->lock); - } - locknum = -1; + sem_wait_array(sma); + return -1; } - return locknum; } static inline void sem_unlock(struct sem_array *sma, int locknum) @@ -876,6 +918,24 @@ again: } /** + * set_semotime(sma, sops) - set sem_otime + * @sma: semaphore array + * @sops: operations that modified the array, may be NULL + * + * sem_otime is replicated to avoid cache line trashing. + * This function sets one instance to the current time. + */ +static void set_semotime(struct sem_array *sma, struct sembuf *sops) +{ + if (sops == NULL) { + sma->sem_base[0].sem_otime = get_seconds(); + } else { + sma->sem_base[sops[0].sem_num].sem_otime = + get_seconds(); + } +} + +/** * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue * @sma: semaphore array * @sops: operations that were performed @@ -925,17 +985,10 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop } } } - if (otime) { - if (sops == NULL) { - sma->sem_base[0].sem_otime = get_seconds(); - } else { - sma->sem_base[sops[0].sem_num].sem_otime = - get_seconds(); - } - } + if (otime) + set_semotime(sma, sops); } - /* The following counts are associated to each semaphore: * semncnt number of tasks waiting on semval being nonzero * semzcnt number of tasks waiting on semval being zero @@ -1229,6 +1282,12 @@ static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, sem_lock(sma, NULL, -1); + if (sma->sem_perm.deleted) { + sem_unlock(sma, -1); + rcu_read_unlock(); + return -EIDRM; + } + curr = &sma->sem_base[semnum]; ipc_assert_locked_object(&sma->sem_perm); @@ -1283,12 +1342,14 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, int i; sem_lock(sma, NULL, -1); + if (sma->sem_perm.deleted) { + err = -EIDRM; + goto out_unlock; + } if(nsems > SEMMSL_FAST) { if (!ipc_rcu_getref(sma)) { - sem_unlock(sma, -1); - rcu_read_unlock(); err = -EIDRM; - goto out_free; + goto out_unlock; } sem_unlock(sma, -1); rcu_read_unlock(); @@ -1301,10 +1362,8 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, rcu_read_lock(); sem_lock_and_putref(sma); if (sma->sem_perm.deleted) { - sem_unlock(sma, -1); - rcu_read_unlock(); err = -EIDRM; - goto out_free; + goto out_unlock; } } for (i = 0; i < sma->sem_nsems; i++) @@ -1322,8 +1381,8 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, struct sem_undo *un; if (!ipc_rcu_getref(sma)) { - rcu_read_unlock(); - return -EIDRM; + err = -EIDRM; + goto out_rcu_wakeup; } rcu_read_unlock(); @@ -1351,10 +1410,8 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, rcu_read_lock(); sem_lock_and_putref(sma); if (sma->sem_perm.deleted) { - sem_unlock(sma, -1); - rcu_read_unlock(); err = -EIDRM; - goto out_free; + goto out_unlock; } for (i = 0; i < nsems; i++) @@ -1378,6 +1435,10 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, goto out_rcu_wakeup; sem_lock(sma, NULL, -1); + if (sma->sem_perm.deleted) { + err = -EIDRM; + goto out_unlock; + } curr = &sma->sem_base[semnum]; switch (cmd) { @@ -1783,6 +1844,10 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, if (error) goto out_rcu_wakeup; + error = -EIDRM; + locknum = sem_lock(sma, sops, nsops); + if (sma->sem_perm.deleted) + goto out_unlock_free; /* * semid identifiers are not unique - find_alloc_undo may have * allocated an undo structure, it was invalidated by an RMID @@ -1790,19 +1855,22 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, * This case can be detected checking un->semid. The existence of * "un" itself is guaranteed by rcu. */ - error = -EIDRM; - locknum = sem_lock(sma, sops, nsops); if (un && un->semid == -1) goto out_unlock_free; error = perform_atomic_semop(sma, sops, nsops, un, task_tgid_vnr(current)); - if (error <= 0) { - if (alter && error == 0) + if (error == 0) { + /* If the operation was successful, then do + * the required updates. + */ + if (alter) do_smart_update(sma, sops, nsops, 1, &tasks); - - goto out_unlock_free; + else + set_semotime(sma, sops); } + if (error <= 0) + goto out_unlock_free; /* We need to sleep on this operation, so we put the current * task into the pending queue and go to sleep. @@ -1999,6 +2067,12 @@ void exit_sem(struct task_struct *tsk) } sem_lock(sma, NULL, -1); + /* exit_sem raced with IPC_RMID, nothing to do */ + if (sma->sem_perm.deleted) { + sem_unlock(sma, -1); + rcu_read_unlock(); + continue; + } un = __lookup_undo(ulp, semid); if (un == NULL) { /* exit_sem raced with IPC_RMID+semget() that created @@ -2061,6 +2135,14 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it) struct sem_array *sma = it; time_t sem_otime; + /* + * The proc interface isn't aware of sem_lock(), it calls + * ipc_lock_object() directly (in sysvipc_find_ipc). + * In order to stay compatible with sem_lock(), we must wait until + * all simple semop() calls have left their critical regions. + */ + sem_wait_array(sma); + sem_otime = get_semotime(sma); return seq_printf(s, diff --git a/ipc/util.c b/ipc/util.c index fdb8ae74077..7684f41bce7 100644 --- a/ipc/util.c +++ b/ipc/util.c @@ -17,12 +17,27 @@ * Pavel Emelianov <xemul@openvz.org> * * General sysv ipc locking scheme: - * when doing ipc id lookups, take the ids->rwsem - * rcu_read_lock() - * obtain the ipc object (kern_ipc_perm) - * perform security, capabilities, auditing and permission checks, etc. - * acquire the ipc lock (kern_ipc_perm.lock) throught ipc_lock_object() - * perform data updates (ie: SET, RMID, LOCK/UNLOCK commands) + * rcu_read_lock() + * obtain the ipc object (kern_ipc_perm) by looking up the id in an idr + * tree. + * - perform initial checks (capabilities, auditing and permission, + * etc). + * - perform read-only operations, such as STAT, INFO commands. + * acquire the ipc lock (kern_ipc_perm.lock) through + * ipc_lock_object() + * - perform data updates, such as SET, RMID commands and + * mechanism-specific operations (semop/semtimedop, + * msgsnd/msgrcv, shmat/shmdt). + * drop the ipc lock, through ipc_unlock_object(). + * rcu_read_unlock() + * + * The ids->rwsem must be taken when: + * - creating, removing and iterating the existing entries in ipc + * identifier sets. + * - iterating through files under /proc/sysvipc/ + * + * Note that sems have a special fast path that avoids kern_ipc_perm.lock - + * see sem_lock(). */ #include <linux/mm.h> |