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ipc: fix GETALL/IPC_RM race for sysv semaphores 

We can step on WARN_ON_ONCE() in sem_getref() if a semaphore is removed
just as we are about to call sem_getref() from semctl_main(); results
are not pretty.

We should fail with -EIDRM, same as if IPC_RM happened while we'd been
doing allocation there.  This also expands sem_getref() at its only
callsite (and fixed there), while sem_getref_and_unlock() is simply
killed off - it has no callers at all.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Al Viro 2013-05-03 00:30:49 +01:00 committed by Linus Torvalds
parent 20a2078ce7
commit ce857229e0
1 changed files with 8 additions and 21 deletions
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29
ipc/sem.c
View File

@ -328,28 +328,12 @@ static inline void sem_lock_and_putref(struct sem_array *sma)
ipc_rcu_putref(sma);
}
static inline void sem_getref_and_unlock(struct sem_array *sma)
{
WARN_ON_ONCE(!ipc_rcu_getref(sma));
sem_unlock(sma, -1);
}
static inline void sem_putref(struct sem_array *sma)
{
sem_lock_and_putref(sma);
sem_unlock(sma, -1);
}
/*
* Call inside the rcu read section.
*/
static inline void sem_getref(struct sem_array *sma)
{
sem_lock(sma, NULL, -1);
WARN_ON_ONCE(!ipc_rcu_getref(sma));
sem_unlock(sma, -1);
}
static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
{
ipc_rmid(&sem_ids(ns), &s->sem_perm);
@ -1116,9 +1100,14 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
ushort __user *array = p;
int i;
sem_lock(sma, NULL, -1);
if(nsems > SEMMSL_FAST) {
sem_getref(sma);
if (!ipc_rcu_getref(sma)) {
sem_unlock(sma, -1);
err = -EIDRM;
goto out_free;
}
sem_unlock(sma, -1);
sem_io = ipc_alloc(sizeof(ushort)*nsems);
if(sem_io == NULL) {
sem_putref(sma);
@ -1131,9 +1120,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
err = -EIDRM;
goto out_free;
}
} else
sem_lock(sma, NULL, -1);
}
for (i = 0; i < sma->sem_nsems; i++)
sem_io[i] = sma->sem_base[i].semval;
sem_unlock(sma, -1);