diff options
Diffstat (limited to 'ipc')
| -rw-r--r-- | ipc/msg.c | 7 | ||||
| -rw-r--r-- | ipc/sem.c | 24 | ||||
| -rw-r--r-- | ipc/shm.c | 16 | ||||
| -rw-r--r-- | ipc/util.h | 13 |
4 files changed, 41 insertions, 19 deletions
diff --git a/ipc/msg.c b/ipc/msg.c index 558aa91186b6..8983ea57d970 100644 --- a/ipc/msg.c +++ b/ipc/msg.c @@ -696,7 +696,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext, goto out_unlock0; /* raced with RMID? */ - if (msq->q_perm.deleted) { + if (!ipc_valid_object(&msq->q_perm)) { err = -EIDRM; goto out_unlock0; } @@ -731,7 +731,8 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext, ipc_lock_object(&msq->q_perm); ipc_rcu_putref(msq, ipc_rcu_free); - if (msq->q_perm.deleted) { + /* raced with RMID? */ + if (!ipc_valid_object(&msq->q_perm)) { err = -EIDRM; goto out_unlock0; } @@ -909,7 +910,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl ipc_lock_object(&msq->q_perm); /* raced with RMID? */ - if (msq->q_perm.deleted) { + if (!ipc_valid_object(&msq->q_perm)) { msg = ERR_PTR(-EIDRM); goto out_unlock0; } diff --git a/ipc/sem.c b/ipc/sem.c index cc9ac35b793c..4d88194a5ffe 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -1284,7 +1284,7 @@ static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, sem_lock(sma, NULL, -1); - if (sma->sem_perm.deleted) { + if (!ipc_valid_object(&sma->sem_perm)) { sem_unlock(sma, -1); rcu_read_unlock(); return -EIDRM; @@ -1344,7 +1344,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, int i; sem_lock(sma, NULL, -1); - if (sma->sem_perm.deleted) { + if (!ipc_valid_object(&sma->sem_perm)) { err = -EIDRM; goto out_unlock; } @@ -1363,7 +1363,7 @@ 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) { + if (!ipc_valid_object(&sma->sem_perm)) { err = -EIDRM; goto out_unlock; } @@ -1411,7 +1411,7 @@ 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) { + if (!ipc_valid_object(&sma->sem_perm)) { err = -EIDRM; goto out_unlock; } @@ -1437,7 +1437,7 @@ 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) { + if (!ipc_valid_object(&sma->sem_perm)) { err = -EIDRM; goto out_unlock; } @@ -1701,7 +1701,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) /* step 3: Acquire the lock on semaphore array */ rcu_read_lock(); sem_lock_and_putref(sma); - if (sma->sem_perm.deleted) { + if (!ipc_valid_object(&sma->sem_perm)) { sem_unlock(sma, -1); rcu_read_unlock(); kfree(new); @@ -1848,7 +1848,15 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, error = -EIDRM; locknum = sem_lock(sma, sops, nsops); - if (sma->sem_perm.deleted) + /* + * We eventually might perform the following check in a lockless + * fashion, considering ipc_valid_object() locking constraints. + * If nsops == 1 and there is no contention for sem_perm.lock, then + * only a per-semaphore lock is held and it's OK to proceed with the + * check below. More details on the fine grained locking scheme + * entangled here and why it's RMID race safe on comments at sem_lock() + */ + if (!ipc_valid_object(&sma->sem_perm)) goto out_unlock_free; /* * semid identifiers are not unique - find_alloc_undo may have @@ -2070,7 +2078,7 @@ 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) { + if (!ipc_valid_object(&sma->sem_perm)) { sem_unlock(sma, -1); rcu_read_unlock(); continue; diff --git a/ipc/shm.c b/ipc/shm.c index 7a51443a51d6..1bc68f115842 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -975,6 +975,13 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf) goto out_unlock1; ipc_lock_object(&shp->shm_perm); + + /* check if shm_destroy() is tearing down shp */ + if (!ipc_valid_object(&shp->shm_perm)) { + err = -EIDRM; + goto out_unlock0; + } + if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) { kuid_t euid = current_euid(); if (!uid_eq(euid, shp->shm_perm.uid) && @@ -989,13 +996,6 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf) } shm_file = shp->shm_file; - - /* check if shm_destroy() is tearing down shp */ - if (shm_file == NULL) { - err = -EIDRM; - goto out_unlock0; - } - if (is_file_hugepages(shm_file)) goto out_unlock0; @@ -1116,7 +1116,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, ipc_lock_object(&shp->shm_perm); /* check if shm_destroy() is tearing down shp */ - if (shp->shm_file == NULL) { + if (!ipc_valid_object(&shp->shm_perm)) { ipc_unlock_object(&shp->shm_perm); err = -EIDRM; goto out_unlock; diff --git a/ipc/util.h b/ipc/util.h index 59d78aa94987..d05b7085a887 100644 --- a/ipc/util.h +++ b/ipc/util.h @@ -185,6 +185,19 @@ static inline void ipc_unlock(struct kern_ipc_perm *perm) rcu_read_unlock(); } +/* + * ipc_valid_object() - helper to sort out IPC_RMID races for codepaths + * where the respective ipc_ids.rwsem is not being held down. + * Checks whether the ipc object is still around or if it's gone already, as + * ipc_rmid() may have already freed the ID while the ipc lock was spinning. + * Needs to be called with kern_ipc_perm.lock held -- exception made for one + * checkpoint case at sys_semtimedop() as noted in code commentary. + */ +static inline bool ipc_valid_object(struct kern_ipc_perm *perm) +{ + return perm->deleted == 0; +} + struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id); int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids, struct ipc_ops *ops, struct ipc_params *params); |