svn commit: r295385 - in head: sys/kern tools/regression/sysvsem

[Jilles Tjoelker]

Author: jilles
Date: Sun Feb  7 22:12:39 2016
New Revision: 295385
URL: https://svnweb.freebsd.org/changeset/base/295385

Log:
  semget(): Check for [EEXIST] error first.
  
  Although POSIX literally permits failing with [EINVAL] if IPC_CREAT and
  IPC_EXCL were both passed, the semaphore set already exists and has fewer
  semaphores than nsems, this does not allow an application to retry safely:
  if the [EINVAL] is actually because of the semmsl limit, an infinite loop
  would result.
  
  PR:		206927

Modified:
  head/sys/kern/sysv_sem.c
  head/tools/regression/sysvsem/semtest.c

Modified: head/sys/kern/sysv_sem.c
==============================================================================
--- head/sys/kern/sysv_sem.c	Sun Feb  7 21:25:08 2016	(r295384)
+++ head/sys/kern/sysv_sem.c	Sun Feb  7 22:12:39 2016	(r295385)
@@ -867,6 +867,11 @@ sys_semget(struct thread *td, struct sem
 		}
 		if (semid < seminfo.semmni) {
 			DPRINTF(("found public key\n"));
+			if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
+				DPRINTF(("not exclusive\n"));
+				error = EEXIST;
+				goto done2;
+			}
 			if ((error = ipcperm(td, &sema[semid].u.sem_perm,
 			    semflg & 0700))) {
 				goto done2;
@@ -876,11 +881,6 @@ sys_semget(struct thread *td, struct sem
 				error = EINVAL;
 				goto done2;
 			}
-			if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
-				DPRINTF(("not exclusive\n"));
-				error = EEXIST;
-				goto done2;
-			}
 #ifdef MAC
 			error = mac_sysvsem_check_semget(cred, &sema[semid]);
 			if (error != 0)

Modified: head/tools/regression/sysvsem/semtest.c
==============================================================================
--- head/tools/regression/sysvsem/semtest.c	Sun Feb  7 21:25:08 2016	(r295384)
+++ head/tools/regression/sysvsem/semtest.c	Sun Feb  7 22:12:39 2016	(r295385)
@@ -152,6 +152,15 @@ main(int argc, char *argv[])
 
 	print_semid_ds(&s_ds, 0600);
 
+	errno = 0;
+	if (semget(semkey, 1, IPC_CREAT | IPC_EXCL | 0600) != -1 ||
+	    errno != EEXIST)
+		err(1, "semget IPC_EXCL 1 did not fail with [EEXIST]");
+	errno = 0;
+	if (semget(semkey, 2, IPC_CREAT | IPC_EXCL | 0600) != -1 ||
+	    errno != EEXIST)
+		err(1, "semget IPC_EXCL 2 did not fail with [EEXIST]");
+
 	for (child_count = 0; child_count < 5; child_count++) {
 		switch ((child_pid = fork())) {
 		case -1: