diff options
| author | Rafael Aquini <aquini@redhat.com> | 2014-01-27 17:07:01 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-01-27 21:02:39 -0800 |
| commit | 0f3d2b0135f4bdbfe47a99753923a64efd373d11 (patch) | |
| tree | 4b211b7502e2412aedd94400bdcb012a2b5814b3 /ipc/sem.c | |
| parent | 78f5009cc35eb5e52d276a046d90ee2f41b60f8c (diff) | |
ipc: introduce ipc_valid_object() helper to sort out IPC_RMID races
After the locking semantics for the SysV IPC API got improved, a couple
of IPC_RMID race windows were opened because we ended up dropping the
'kern_ipc_perm.deleted' check performed way down in ipc_lock(). The
spotted races got sorted out by re-introducing the old test within the
racy critical sections.
This patch introduces ipc_valid_object() to consolidate the way we cope
with IPC_RMID races by using the same abstraction across the API
implementation.
Signed-off-by: Rafael Aquini <aquini@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Greg Thelen <gthelen@google.com>
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/sem.c')
| -rw-r--r-- | ipc/sem.c | 24 |
1 files changed, 16 insertions, 8 deletions
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; |