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-rw-r--r--include/linux/sem.h12
-rw-r--r--ipc/sem.c163
2 files changed, 95 insertions, 80 deletions
diff --git a/include/linux/sem.h b/include/linux/sem.h
index c8eaad9e4b7..6a1af1b49a1 100644
--- a/include/linux/sem.h
+++ b/include/linux/sem.h
@@ -95,7 +95,7 @@ struct sem_array {
struct sem *sem_base; /* ptr to first semaphore in array */
struct sem_queue *sem_pending; /* pending operations to be processed */
struct sem_queue **sem_pending_last; /* last pending operation */
- struct sem_undo *undo; /* undo requests on this array */
+ struct list_head list_id; /* undo requests on this array */
unsigned long sem_nsems; /* no. of semaphores in array */
};
@@ -118,8 +118,8 @@ struct sem_queue {
* when the process exits.
*/
struct sem_undo {
- struct sem_undo * proc_next; /* next entry on this process */
- struct sem_undo * id_next; /* next entry on this semaphore set */
+ struct list_head list_proc; /* per-process list: all undos from one process */
+ struct list_head list_id; /* per semaphore array list: all undos for one array */
int semid; /* semaphore set identifier */
short * semadj; /* array of adjustments, one per semaphore */
};
@@ -128,9 +128,9 @@ struct sem_undo {
* that may be shared among all a CLONE_SYSVSEM task group.
*/
struct sem_undo_list {
- atomic_t refcnt;
- spinlock_t lock;
- struct sem_undo *proc_list;
+ atomic_t refcnt;
+ spinlock_t lock;
+ struct list_head list_proc;
};
struct sysv_sem {
diff --git a/ipc/sem.c b/ipc/sem.c
index e9418df5ff3..4f26c715735 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -274,7 +274,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
sma->sem_base = (struct sem *) &sma[1];
/* sma->sem_pending = NULL; */
sma->sem_pending_last = &sma->sem_pending;
- /* sma->undo = NULL; */
+ INIT_LIST_HEAD(&sma->list_id);
sma->sem_nsems = nsems;
sma->sem_ctime = get_seconds();
sem_unlock(sma);
@@ -536,7 +536,8 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
* (They will be freed without any further action in exit_sem()
* or during the next semop.)
*/
- for (un = sma->undo; un; un = un->id_next)
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_for_each_entry(un, &sma->list_id, list_id)
un->semid = -1;
/* Wake up all pending processes and let them fail with EIDRM. */
@@ -763,9 +764,12 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
for (i = 0; i < nsems; i++)
sma->sem_base[i].semval = sem_io[i];
- for (un = sma->undo; un; un = un->id_next)
+
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_for_each_entry(un, &sma->list_id, list_id) {
for (i = 0; i < nsems; i++)
un->semadj[i] = 0;
+ }
sma->sem_ctime = get_seconds();
/* maybe some queued-up processes were waiting for this */
update_queue(sma);
@@ -797,12 +801,15 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
{
int val = arg.val;
struct sem_undo *un;
+
err = -ERANGE;
if (val > SEMVMX || val < 0)
goto out_unlock;
- for (un = sma->undo; un; un = un->id_next)
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_for_each_entry(un, &sma->list_id, list_id)
un->semadj[semnum] = 0;
+
curr->semval = val;
curr->sempid = task_tgid_vnr(current);
sma->sem_ctime = get_seconds();
@@ -952,6 +959,8 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp)
return -ENOMEM;
spin_lock_init(&undo_list->lock);
atomic_set(&undo_list->refcnt, 1);
+ INIT_LIST_HEAD(&undo_list->list_proc);
+
current->sysvsem.undo_list = undo_list;
}
*undo_listp = undo_list;
@@ -960,25 +969,30 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp)
static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
{
- struct sem_undo **last, *un;
-
- last = &ulp->proc_list;
- un = *last;
- while(un != NULL) {
- if(un->semid==semid)
- break;
- if(un->semid==-1) {
- *last=un->proc_next;
- kfree(un);
- } else {
- last=&un->proc_next;
+ struct sem_undo *walk, *tmp;
+
+ assert_spin_locked(&ulp->lock);
+ list_for_each_entry_safe(walk, tmp, &ulp->list_proc, list_proc) {
+ if (walk->semid == semid)
+ return walk;
+ if (walk->semid == -1) {
+ list_del(&walk->list_proc);
+ kfree(walk);
}
- un=*last;
}
- return un;
+ return NULL;
}
-static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
+/**
+ * find_alloc_undo - Lookup (and if not present create) undo array
+ * @ns: namespace
+ * @semid: semaphore array id
+ *
+ * The function looks up (and if not present creates) the undo structure.
+ * The size of the undo structure depends on the size of the semaphore
+ * array, thus the alloc path is not that straightforward.
+ */
+static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
{
struct sem_array *sma;
struct sem_undo_list *ulp;
@@ -997,6 +1011,7 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
goto out;
/* no undo structure around - allocate one. */
+ /* step 1: figure out the size of the semaphore array */
sma = sem_lock_check(ns, semid);
if (IS_ERR(sma))
return ERR_PTR(PTR_ERR(sma));
@@ -1004,15 +1019,19 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
nsems = sma->sem_nsems;
sem_getref_and_unlock(sma);
+ /* step 2: allocate new undo structure */
new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
if (!new) {
sem_putref(sma);
return ERR_PTR(-ENOMEM);
}
- new->semadj = (short *) &new[1];
- new->semid = semid;
+ /* step 3: Acquire the lock on the undo list pointer */
spin_lock(&ulp->lock);
+
+ /* step 4: check for races: someone else allocated the undo struct,
+ * semaphore array was destroyed.
+ */
un = lookup_undo(ulp, semid);
if (un) {
spin_unlock(&ulp->lock);
@@ -1028,13 +1047,17 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
un = ERR_PTR(-EIDRM);
goto out;
}
- new->proc_next = ulp->proc_list;
- ulp->proc_list = new;
- new->id_next = sma->undo;
- sma->undo = new;
+ /* step 5: initialize & link new undo structure */
+ new->semadj = (short *) &new[1];
+ new->semid = semid;
+ assert_spin_locked(&ulp->lock);
+ list_add(&new->list_proc, &ulp->list_proc);
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_add(&new->list_id, &sma->list_id);
+
sem_unlock(sma);
- un = new;
spin_unlock(&ulp->lock);
+ un = new;
out:
return un;
}
@@ -1090,9 +1113,8 @@ asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
alter = 1;
}
-retry_undos:
if (undos) {
- un = find_undo(ns, semid);
+ un = find_alloc_undo(ns, semid);
if (IS_ERR(un)) {
error = PTR_ERR(un);
goto out_free;
@@ -1107,14 +1129,14 @@ retry_undos:
}
/*
- * semid identifiers are not unique - find_undo may have
+ * semid identifiers are not unique - find_alloc_undo may have
* allocated an undo structure, it was invalidated by an RMID
- * and now a new array with received the same id. Check and retry.
+ * and now a new array with received the same id. Check and fail.
*/
- if (un && un->semid == -1) {
- sem_unlock(sma);
- goto retry_undos;
- }
+ error = -EIDRM;
+ if (un && un->semid == -1)
+ goto out_unlock_free;
+
error = -EFBIG;
if (max >= sma->sem_nsems)
goto out_unlock_free;
@@ -1243,56 +1265,44 @@ int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
*/
void exit_sem(struct task_struct *tsk)
{
- struct sem_undo_list *undo_list;
- struct sem_undo *u, **up;
- struct ipc_namespace *ns;
+ struct sem_undo_list *ulp;
+ struct sem_undo *un, *tmp;
- undo_list = tsk->sysvsem.undo_list;
- if (!undo_list)
+ ulp = tsk->sysvsem.undo_list;
+ if (!ulp)
return;
tsk->sysvsem.undo_list = NULL;
- if (!atomic_dec_and_test(&undo_list->refcnt))
+ if (!atomic_dec_and_test(&ulp->refcnt))
return;
- ns = tsk->nsproxy->ipc_ns;
- /* There's no need to hold the semundo list lock, as current
- * is the last task exiting for this undo list.
- */
- for (up = &undo_list->proc_list; (u = *up); *up = u->proc_next, kfree(u)) {
+ spin_lock(&ulp->lock);
+
+ list_for_each_entry_safe(un, tmp, &ulp->list_proc, list_proc) {
struct sem_array *sma;
- int nsems, i;
- struct sem_undo *un, **unp;
- int semid;
-
- semid = u->semid;
-
- if(semid == -1)
- continue;
- sma = sem_lock(ns, semid);
+ int i;
+
+ if (un->semid == -1)
+ goto free;
+
+ sma = sem_lock(tsk->nsproxy->ipc_ns, un->semid);
if (IS_ERR(sma))
- continue;
+ goto free;
- if (u->semid == -1)
- goto next_entry;
+ if (un->semid == -1)
+ goto unlock_free;
- BUG_ON(sem_checkid(sma, u->semid));
+ BUG_ON(sem_checkid(sma, un->semid));
- /* remove u from the sma->undo list */
- for (unp = &sma->undo; (un = *unp); unp = &un->id_next) {
- if (u == un)
- goto found;
- }
- printk ("exit_sem undo list error id=%d\n", u->semid);
- goto next_entry;
-found:
- *unp = un->id_next;
- /* perform adjustments registered in u */
- nsems = sma->sem_nsems;
- for (i = 0; i < nsems; i++) {
+ /* remove un from sma->list_id */
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_del(&un->list_id);
+
+ /* perform adjustments registered in un */
+ for (i = 0; i < sma->sem_nsems; i++) {
struct sem * semaphore = &sma->sem_base[i];
- if (u->semadj[i]) {
- semaphore->semval += u->semadj[i];
+ if (un->semadj[i]) {
+ semaphore->semval += un->semadj[i];
/*
* Range checks of the new semaphore value,
* not defined by sus:
@@ -1316,10 +1326,15 @@ found:
sma->sem_otime = get_seconds();
/* maybe some queued-up processes were waiting for this */
update_queue(sma);
-next_entry:
+unlock_free:
sem_unlock(sma);
+free:
+ assert_spin_locked(&ulp->lock);
+ list_del(&un->list_proc);
+ kfree(un);
}
- kfree(undo_list);
+ spin_unlock(&ulp->lock);
+ kfree(ulp);
}
#ifdef CONFIG_PROC_FS
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-12-14 12:24:48 +0000