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Merge pull request #2527 from brauner/2018-08-15/file_lock_fixes

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lxccontainer: improve file locking
This commit is contained in:
Stéphane Graber 2018-08-14 23:23:24 -04:00 committed by GitHub
commit c43e9ced75
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 52 additions and 36 deletions
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16
src/lxc/lxccontainer.c
View File

@ -155,12 +155,13 @@ static int ongoing_create(struct lxc_container *c)
if (ret < 0 || (size_t)ret >= len)
return -1;
if (!file_exists(path))
return 0;
fd = open(path, O_RDWR | O_CLOEXEC);
if (fd < 0) {
if (errno != ENOENT)
return -1;
fd = open(path, O_RDWR);
if (fd < 0)
return 0;
}
lk.l_type = F_WRLCK;
lk.l_whence = SEEK_SET;
@ -170,8 +171,11 @@ static int ongoing_create(struct lxc_container *c)
lk.l_pid = 0;
ret = fcntl(fd, F_OFD_GETLK, &lk);
if (ret < 0 && errno == EINVAL)
if (ret < 0 && errno == EINVAL) {
ret = flock(fd, LOCK_EX | LOCK_NB);
if (ret < 0 && errno == EWOULDBLOCK)
ret = 0;
}
close(fd);
@ -198,7 +202,7 @@ static int create_partial(struct lxc_container *c)
if (ret < 0 || (size_t)ret >= len)
return -1;
fd = open(path, O_RDWR | O_CREAT | O_EXCL, 0755);
fd = open(path, O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0000);
if (fd < 0)
return -1;

72
src/lxc/lxclock.c
View File

@ -96,9 +96,8 @@ static void unlock_mutex(pthread_mutex_t *l)
static char *lxclock_name(const char *p, const char *n)
{
int ret;
int len;
char *dest;
char *rundir;
size_t len;
char *dest, *rundir;
/* lockfile will be:
* "/run" + "/lxc/lock/$lxcpath/$lxcname + '\0' if root
@ -107,20 +106,22 @@ static char *lxclock_name(const char *p, const char *n)
*/
/* length of "/lxc/lock/" + $lxcpath + "/" + "." + $lxcname + '\0' */
len = strlen("/lxc/lock/") + strlen(n) + strlen(p) + 3;
len = (sizeof("/lxc/lock/") - 1) + strlen(n) + strlen(p) + 3;
rundir = get_rundir();
if (!rundir)
return NULL;
len += strlen(rundir);
if ((dest = malloc(len)) == NULL) {
dest = malloc(len);
if (!dest) {
free(rundir);
return NULL;
}
ret = snprintf(dest, len, "%s/lxc/lock/%s", rundir, p);
if (ret < 0 || ret >= len) {
if (ret < 0 || (size_t)ret >= len) {
free(dest);
free(rundir);
return NULL;
@ -135,7 +136,7 @@ static char *lxclock_name(const char *p, const char *n)
ret = snprintf(dest, len, "%s/lxc/lock/%s/.%s", rundir, p, n);
free(rundir);
if (ret < 0 || ret >= len) {
if (ret < 0 || (size_t)ret >= len) {
free(dest);
return NULL;
}
@ -145,15 +146,15 @@ static char *lxclock_name(const char *p, const char *n)
static sem_t *lxc_new_unnamed_sem(void)
{
sem_t *s;
int ret;
sem_t *s;
s = malloc(sizeof(*s));
if (!s)
return NULL;
ret = sem_init(s, 0, 1);
if (ret) {
if (ret < 0) {
free(s);
return NULL;
}
@ -167,7 +168,7 @@ struct lxc_lock *lxc_newlock(const char *lxcpath, const char *name)
l = malloc(sizeof(*l));
if (!l)
goto out;
goto on_error;
if (!name) {
l->type = LXC_LOCK_ANON_SEM;
@ -177,7 +178,7 @@ struct lxc_lock *lxc_newlock(const char *lxcpath, const char *name)
l = NULL;
}
goto out;
goto on_error;
}
l->type = LXC_LOCK_FLOCK;
@ -185,19 +186,19 @@ struct lxc_lock *lxc_newlock(const char *lxcpath, const char *name)
if (!l->u.f.fname) {
free(l);
l = NULL;
goto out;
goto on_error;
}
l->u.f.fd = -1;
out:
on_error:
return l;
}
int lxclock(struct lxc_lock *l, int timeout)
{
int ret = -1, saved_errno = errno;
struct flock lk;
int ret = -1, saved_errno = errno;
switch(l->type) {
case LXC_LOCK_ANON_SEM:
@ -208,9 +209,10 @@ int lxclock(struct lxc_lock *l, int timeout)
} else {
struct timespec ts;
if (clock_gettime(CLOCK_REALTIME, &ts) == -1) {
ret = clock_gettime(CLOCK_REALTIME, &ts);
if (ret < 0) {
ret = -2;
goto out;
goto on_error;
}
ts.tv_sec += timeout;
@ -218,25 +220,26 @@ int lxclock(struct lxc_lock *l, int timeout)
if (ret < 0)
saved_errno = errno;
}
break;
case LXC_LOCK_FLOCK:
ret = -2;
if (timeout) {
ERROR("Error: timeout not supported with flock");
goto out;
ERROR("Timeouts are not supported with file locks");
goto on_error;
}
if (!l->u.f.fname) {
ERROR("Error: filename not set for flock");
goto out;
ERROR("No filename set for file lock");
goto on_error;
}
if (l->u.f.fd == -1) {
l->u.f.fd = open(l->u.f.fname, O_CREAT | O_RDWR | O_NOFOLLOW | O_CLOEXEC | O_NOCTTY, S_IWUSR | S_IRUSR);
if (l->u.f.fd == -1) {
ERROR("Error opening %s", l->u.f.fname);
SYSERROR("Failed to open \"%s\"", l->u.f.fname);
saved_errno = errno;
goto out;
goto on_error;
}
}
@ -251,27 +254,29 @@ int lxclock(struct lxc_lock *l, int timeout)
ret = flock(l->u.f.fd, LOCK_EX);
saved_errno = errno;
}
break;
}
out:
on_error:
errno = saved_errno;
return ret;
}
int lxcunlock(struct lxc_lock *l)
{
int ret = 0, saved_errno = errno;
struct flock lk;
int ret = 0, saved_errno = errno;
switch(l->type) {
switch (l->type) {
case LXC_LOCK_ANON_SEM:
if (!l->u.sem)
if (!l->u.sem) {
ret = -2;
else {
} else {
ret = sem_post(l->u.sem);
saved_errno = errno;
}
break;
case LXC_LOCK_FLOCK:
if (l->u.f.fd != -1) {
@ -289,8 +294,10 @@ int lxcunlock(struct lxc_lock *l)
close(l->u.f.fd);
l->u.f.fd = -1;
} else
} else {
ret = -2;
}
break;
}
@ -317,6 +324,7 @@ void lxc_putlock(struct lxc_lock *l)
free(l->u.sem);
l->u.sem = NULL;
}
break;
case LXC_LOCK_FLOCK:
if (l->u.f.fd != -1) {
@ -326,8 +334,10 @@ void lxc_putlock(struct lxc_lock *l)
free(l->u.f.fname);
l->u.f.fname = NULL;
break;
}
free(l);
}
@ -355,10 +365,12 @@ int container_disk_lock(struct lxc_container *c)
{
int ret;
if ((ret = lxclock(c->privlock, 0)))
ret = lxclock(c->privlock, 0);
if (ret < 0)
return ret;
if ((ret = lxclock(c->slock, 0))) {
ret = lxclock(c->slock, 0);
if (ret < 0) {
lxcunlock(c->privlock);
return ret;
}