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semget(): Check for [EEXIST] error first.

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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
This commit is contained in:
Jilles Tjoelker 2016-02-07 22:12:39 +00:00
parent 9ef7a36255
commit f00fb5457e
2 changed files with 14 additions and 5 deletions
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10
sys/kern/sysv_sem.c
View File

@ -867,6 +867,11 @@ sys_semget(struct thread *td, struct semget_args *uap)
}
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 semget_args *uap)
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)

9
tools/regression/sysvsem/semtest.c
View File

@ -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: