OS-5223 removed shm segment is no longer available

Reviewed by: Bryan Cantrill <bryan@joyent.com>
Reviewed by: Patrick Mooney <patrick.mooney@joyent.com>

2 files changed, 58 insertions, 9 deletions

diff --git a/usr/src/uts/common/os/ipc.c b/usr/src/uts/common/os/ipc.c
index 9381019cd1..6a6f5d84ef 100644
--- a/usr/src/uts/common/os/ipc.c
+++ b/usr/src/uts/common/os/ipc.c
@@ -20,6 +20,7 @@
  */
 /*
  * Copyright (c) 1988, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2016 Joyent, Inc.
  */
 
 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T		*/
@@ -1217,6 +1218,23 @@ ipc_remove(ipc_service_t *service, kipc_perm_t *perm)
 	    (IPC_ZONE_USAGE(perm, service) == 0)));
 }
 
+/*
+ * Perform actual IPC_RMID, either via ipc_rmid or due to a delayed *_RMID.
+ */
+void
+ipc_rmsvc(ipc_service_t *service, kipc_perm_t *perm)
+{
+	ASSERT(service->ipcs_count > 0);
+	ASSERT(MUTEX_HELD(&service->ipcs_lock));
+
+	ipc_remove(service, perm);
+	mutex_exit(&service->ipcs_lock);
+
+	/* perform any per-service removal actions */
+	service->ipcs_rmid(perm);
+
+	ipc_rele(service, perm);
+}
 
 /*
  * Common code to perform an IPC_RMID.  Returns an errno value on
@@ -1247,13 +1265,7 @@ ipc_rmid(ipc_service_t *service, int id, cred_t *cr)
 	/*
 	 * Nothing can fail from this point on.
 	 */
-	ipc_remove(service, perm);
-	mutex_exit(&service->ipcs_lock);
-
-	/* perform any per-service removal actions */
-	service->ipcs_rmid(perm);
-
-	ipc_rele(service, perm);
+	ipc_rmsvc(service, perm);
 
 	return (0);
 }
diff --git a/usr/src/uts/common/os/shm.c b/usr/src/uts/common/os/shm.c
index bacc595f78..5deae96d73 100644
--- a/usr/src/uts/common/os/shm.c
+++ b/usr/src/uts/common/os/shm.c
@@ -21,6 +21,7 @@
 
 /*
  * Copyright (c) 1986, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2016 Joyent, Inc.
  */
 
 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
@@ -319,6 +320,7 @@ shmat(int shmid, caddr_t uaddr, int uflags, uintptr_t *rvp)
 		size_t	share_size;
 		struct	shm_data ssd;
 		uintptr_t align_hint;
+		long	curprot;
 
 		/*
 		 * Pick a share pagesize to use, if (!isspt(sp)).
@@ -453,6 +455,7 @@ shmat(int shmid, caddr_t uaddr, int uflags, uintptr_t *rvp)
 			}
 		}
 
+		curprot = sp->shm_opts & SHM_PROT_MASK;
 		if (!isspt(sp)) {
 			error = sptcreate(size, &segspt, sp->shm_amp, prot,
 			    flags, share_szc);
@@ -462,8 +465,8 @@ shmat(int shmid, caddr_t uaddr, int uflags, uintptr_t *rvp)
 			}
 			sp->shm_sptinfo->sptas = segspt->s_as;
 			sp->shm_sptseg = segspt;
-			sp->shm_sptprot = prot;
-		} else if ((prot & sp->shm_sptprot) != sp->shm_sptprot) {
+			sp->shm_opts = (sp->shm_opts & ~SHM_PROT_MASK) | prot;
+		} else if ((prot & curprot) != curprot) {
 			/*
 			 * Ensure we're attaching to an ISM segment with
 			 * fewer or equal permissions than what we're
@@ -748,6 +751,23 @@ shmctl(int shmid, int cmd, void *arg)
 		}
 		break;
 
+	/* Stage segment for removal, but don't remove until last detach */
+	case SHM_RMID:
+		if ((error = secpolicy_ipc_owner(cr, (kipc_perm_t *)sp)) != 0)
+			break;
+
+		/*
+		 * If attached, just mark it as a pending remove, otherwise
+		 * we must perform the normal ipc_rmid now.
+		 */
+		if ((sp->shm_perm.ipc_ref - 1) > 0) {
+			sp->shm_opts |= SHM_RM_PENDING;
+		} else {
+			mutex_exit(lock);
+			return (ipc_rmid(shm_svc, shmid, cr));
+		}
+		break;
+
 	default:
 		error = EINVAL;
 		break;
@@ -778,6 +798,23 @@ shm_detach(proc_t *pp, segacct_t *sap)
 		sp->shm_ismattch--;
 	sp->shm_dtime = gethrestime_sec();
 	sp->shm_lpid = pp->p_pid;
+	if ((sp->shm_opts & SHM_RM_PENDING) != 0 &&
+	    sp->shm_perm.ipc_ref == 2) {
+		/*
+		 * If this is the last detach of the segment across the whole
+		 * system then now we can perform the delayed IPC_RMID.
+		 * The ipc_ref count has 1 for the original 'get' and one for
+		 * each 'attach' (see 'stat' handling in shmctl).
+		 */
+		sp->shm_opts &= ~SHM_RM_PENDING;
+		mutex_enter(&shm_svc->ipcs_lock);
+		ipc_rmsvc(shm_svc, (kipc_perm_t *)sp);	/* Drops lock */
+		ASSERT(!MUTEX_HELD(&shm_svc->ipcs_lock));
+		ASSERT(((kipc_perm_t *)sp)->ipc_ref > 0);
+
+		/* Lock was dropped, need to retake it for following rele. */
+		(void) ipc_lock(shm_svc, sp->shm_perm.ipc_id);
+	}
 	ipc_rele(shm_svc, (kipc_perm_t *)sp);	/* Drops lock */
 
 	kmem_free(sap, sizeof (segacct_t));