OS-5223 removed shm segment is no longer available

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

7 files changed, 88 insertions, 15 deletions

diff --git a/usr/src/cmd/mdb/common/modules/ipc/ipc.c b/usr/src/cmd/mdb/common/modules/ipc/ipc.c
index 5871e45dd9..7054f59477 100644
--- a/usr/src/cmd/mdb/common/modules/ipc/ipc.c
+++ b/usr/src/cmd/mdb/common/modules/ipc/ipc.c
@@ -21,6 +21,7 @@
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright 2016 Joyent, Inc.
  */
 
 #include <mdb/mdb_modapi.h>
@@ -229,7 +230,9 @@ shm_print(kshmid_t *shmid, uintptr_t addr)
 	printtime_nice("ctime: ", shmid->shm_ctime);
 	mdb_printf("sptinfo: %-?p    sptseg: %-?p\n",
 	    shmid->shm_sptinfo, shmid->shm_sptseg);
-	mdb_printf("sptprot: <%lb>\n", shmid->shm_sptprot, prot_flag_bits);
+	mdb_printf("opts: rmpend: %d prot: <%b>\n",
+	    ((shmid->shm_opts & SHM_RM_PENDING) != 0),
+	    (shmid->shm_opts & SHM_PROT_MASK), prot_flag_bits);
 }
 
 
diff --git a/usr/src/lib/brand/lx/lx_brand/common/sysv_ipc.c b/usr/src/lib/brand/lx/lx_brand/common/sysv_ipc.c
index 665d4ce0a7..99cc12704e 100644
--- a/usr/src/lib/brand/lx/lx_brand/common/sysv_ipc.c
+++ b/usr/src/lib/brand/lx/lx_brand/common/sysv_ipc.c
@@ -21,7 +21,7 @@
 /*
  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
- * Copyright 2015 Joyent, Inc.  All rights reserved.
+ * Copyright 2016 Joyent, Inc.  All rights reserved.
  */
 
 #include <errno.h>
@@ -47,6 +47,9 @@
 #define	SLOT_SHM	1
 #define	SLOT_MSG	2
 
+/* Use private SHM_RMID interface for IPC_RMID */
+#define	SHM_RMID	5
+
 static int
 get_rctlval(rctlblk_t *rblk, char *name, ulong_t limit, uint64_t *val)
 {
@@ -845,7 +848,7 @@ lx_shmctl(int shmid, int cmd, void *buf)
 	switch (cmd & ~LX_IPC_64) {
 	case LX_IPC_RMID:
 		use_errno = 1;
-		r = shmctl(shmid, IPC_RMID, NULL);
+		r = shmctl(shmid, SHM_RMID, NULL);	/* lx-private cmd */
 		break;
 
 	case LX_IPC_SET:
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));
diff --git a/usr/src/uts/common/sys/ipc_impl.h b/usr/src/uts/common/sys/ipc_impl.h
index 0569c3e967..d7dc365c09 100644
--- a/usr/src/uts/common/sys/ipc_impl.h
+++ b/usr/src/uts/common/sys/ipc_impl.h
@@ -20,6 +20,7 @@
  */
 /*
  * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2016, Joyent, Inc.
  */
 
 #ifndef	_IPC_IMPL_H
@@ -226,6 +227,7 @@ int ipc_commit_begin(ipc_service_t *, key_t, int, kipc_perm_t *);
 kmutex_t *ipc_commit_end(ipc_service_t *, kipc_perm_t *);
 void ipc_cleanup(ipc_service_t *, kipc_perm_t *);
 
+void ipc_rmsvc(ipc_service_t *, kipc_perm_t *);
 int ipc_rmid(ipc_service_t *, int, cred_t *);
 int ipc_ids(ipc_service_t *, int *, uint_t, uint_t *);
 
diff --git a/usr/src/uts/common/sys/shm.h b/usr/src/uts/common/sys/shm.h
index e3bd2a77d3..030379488f 100644
--- a/usr/src/uts/common/sys/shm.h
+++ b/usr/src/uts/common/sys/shm.h
@@ -21,6 +21,7 @@
  */
 /*
  * Copyright 2014 Garrett D'Amore <garrett@damore.org>
+ * Copyright 2016 Joyent, Inc.
  *
  * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
@@ -120,6 +121,10 @@ struct shmid_ds {
 #define	SHM_LOCK	3	/* Lock segment in core */
 #define	SHM_UNLOCK	4	/* Unlock segment */
 
+#if defined(_KERNEL)
+#define	SHM_RMID	5	/* Private RMID for lx support */
+#endif
+
 #if !defined(_KERNEL)
 int shmget(key_t, size_t, int);
 int shmids(int *, uint_t, uint_t *);
diff --git a/usr/src/uts/common/sys/shm_impl.h b/usr/src/uts/common/sys/shm_impl.h
index 4d8cdcede5..1eae2ca0a4 100644
--- a/usr/src/uts/common/sys/shm_impl.h
+++ b/usr/src/uts/common/sys/shm_impl.h
@@ -21,13 +21,12 @@
 /*
  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright 2016 Joyent, Inc.
  */
 
 #ifndef	_SYS_SHM_IMPL_H
 #define	_SYS_SHM_IMPL_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/ipc_impl.h>
 #if defined(_KERNEL) || defined(_KMEMUSER)
 #include <sys/shm.h>
@@ -70,7 +69,11 @@ typedef struct kshmid {
 	time_t		shm_ctime;	/* last change time */
 	struct sptinfo	*shm_sptinfo;	/* info about ISM segment */
 	struct seg	*shm_sptseg;	/* pointer to ISM segment */
-	long		shm_sptprot;	/* was reserved (still a "long") */
+	ulong_t		shm_opts;
+					/*
+					 * Composed of: sptprot (uchar_t) and
+					 * RM_PENDING flag (1 bit).
+					 */
 } kshmid_t;
 
 /*
@@ -78,6 +81,14 @@ typedef struct kshmid {
  */
 #define	SHMSA_ISM	1	/* uses shared page table */
 
+/*
+ * shm_opts definitions
+ * Low byte in shm_opts is used for sptprot (see PROT_ALL). The upper bits are
+ * used for additional options.
+ */
+#define	SHM_PROT_MASK	0xff
+#define	SHM_RM_PENDING	0x100
+
 typedef struct sptinfo {
 	struct as	*sptas;		/* dummy as ptr. for spt segment */
 } sptinfo_t;