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Invalidate the cache for the named posix semaphore when opened and

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actual file storing the semaphore object is different from the file
created on the first open.  Store the file st_dev and st_ino members
of the struct stat in the semaphore structure on open, and compare
them with the attributes of the opened file to detect unlink and
re-creation.

This fixes an issue of sem_unlink(3) failing to flush the named entry
in the semaphore list for the current or remote process, making
sem_unlink(3) not correctly operating if the unlinked semaphore is
still opened.

Reported by:	Joris Giovannangeli <joris@giovannangeli.fr>
PR:	standards/189353
Reviewed by:	jilles (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2014-05-10 19:08:07 +00:00
parent 8207fd5f81
commit ca5e4fe970
1 changed files with 38 additions and 31 deletions
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69
lib/libc/gen/sem_new.c
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@ -66,6 +66,8 @@ __weak_reference(_sem_wait, sem_wait);
struct sem_nameinfo {
int open_count;
char *name;
dev_t dev;
ino_t ino;
sem_t *sem;
LIST_ENTRY(sem_nameinfo) next;
};
@ -151,36 +153,45 @@ _sem_open(const char *name, int flags, ...)
return (SEM_FAILED);
}
name++;
strcpy(path, SEM_PREFIX);
if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
errno = ENAMETOOLONG;
return (SEM_FAILED);
}
if (flags & ~(O_CREAT|O_EXCL)) {
errno = EINVAL;
return (SEM_FAILED);
}
_pthread_once(&once, sem_module_init);
_pthread_mutex_lock(&sem_llock);
LIST_FOREACH(ni, &sem_list, next) {
if (strcmp(name, ni->name) == 0) {
if ((flags & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL)) {
_pthread_mutex_unlock(&sem_llock);
errno = EEXIST;
return (SEM_FAILED);
} else {
ni->open_count++;
sem = ni->sem;
_pthread_mutex_unlock(&sem_llock);
return (sem);
}
}
}
if (flags & O_CREAT) {
if ((flags & O_CREAT) != 0) {
va_start(ap, flags);
mode = va_arg(ap, int);
value = va_arg(ap, int);
va_end(ap);
}
fd = -1;
_pthread_once(&once, sem_module_init);
_pthread_mutex_lock(&sem_llock);
LIST_FOREACH(ni, &sem_list, next) {
if (ni->name != NULL && strcmp(name, ni->name) == 0) {
fd = _open(path, flags | O_RDWR | O_CLOEXEC |
O_EXLOCK, mode);
if (fd == -1 || _fstat(fd, &sb) == -1)
goto error;
if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT |
O_EXCL) || ni->dev != sb.st_dev ||
ni->ino != sb.st_ino) {
ni->name = NULL;
ni = NULL;
break;
}
ni->open_count++;
sem = ni->sem;
_pthread_mutex_unlock(&sem_llock);
_close(fd);
return (sem);
}
}
len = sizeof(*ni) + strlen(name) + 1;
ni = (struct sem_nameinfo *)malloc(len);
@ -192,17 +203,11 @@ _sem_open(const char *name, int flags, ...)
ni->name = (char *)(ni+1);
strcpy(ni->name, name);
strcpy(path, SEM_PREFIX);
if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
errno = ENAMETOOLONG;
goto error;
if (fd == -1) {
fd = _open(path, flags | O_RDWR | O_CLOEXEC | O_EXLOCK, mode);
if (fd == -1 || _fstat(fd, &sb) == -1)
goto error;
}
fd = _open(path, flags|O_RDWR|O_CLOEXEC|O_EXLOCK, mode);
if (fd == -1)
goto error;
if (_fstat(fd, &sb))
goto error;
if (sb.st_size < sizeof(sem_t)) {
sem_t tmp;
@ -228,6 +233,8 @@ _sem_open(const char *name, int flags, ...)
}
ni->open_count = 1;
ni->sem = sem;
ni->dev = sb.st_dev;
ni->ino = sb.st_ino;
LIST_INSERT_HEAD(&sem_list, ni, next);
_close(fd);
_pthread_mutex_unlock(&sem_llock);