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commonio: Use do_lock_file again

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This avoids regressions introduced with do_fcntl_lock.

Signed-off-by: Samanta Navarro <ferivoz@riseup.net>
This commit is contained in:
Samanta Navarro 2023-05-10 11:57:20 +00:00 committed by Serge Hallyn
parent 4abcbb056e
commit 72290ede0e
1 changed files with 175 additions and 28 deletions
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203
lib/commonio.c
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@ -34,6 +34,8 @@
/* local function prototypes */
static int lrename (const char *, const char *);
static int check_link_count (const char *file, bool log);
static int do_lock_file (const char *file, const char *lock, bool log);
static /*@null@*/ /*@dependent@*/FILE *fopen_set_perms (
const char *name,
const char *mode,
@ -91,6 +93,150 @@ int lrename (const char *old, const char *new)
return res;
}
static int check_link_count (const char *file, bool log)
{
struct stat sb;
if (stat (file, &sb) != 0) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: %s file stat error: %s\n",
shadow_progname, file, strerror (errno));
}
return 0;
}
if (sb.st_nlink != 2) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: %s: lock file already used (nlink: %u)\n",
shadow_progname, file, sb.st_nlink);
}
return 0;
}
return 1;
}
static int do_lock_file (const char *file, const char *lock, bool log)
{
int fd;
pid_t pid;
ssize_t len;
int retval;
char buf[32];
fd = open (file, O_CREAT | O_TRUNC | O_WRONLY, 0600);
if (-1 == fd) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: %s: %s\n",
shadow_progname, file, strerror (errno));
}
return 0;
}
pid = getpid ();
snprintf (buf, sizeof buf, "%lu", (unsigned long) pid);
len = (ssize_t) strlen (buf) + 1;
if (write (fd, buf, (size_t) len) != len) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: %s file write error: %s\n",
shadow_progname, file, strerror (errno));
}
(void) close (fd);
unlink (file);
return 0;
}
if (fdatasync (fd) == -1) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: %s file sync error: %s\n",
shadow_progname, file, strerror (errno));
}
(void) close (fd);
unlink (file);
return 0;
}
close (fd);
if (link (file, lock) == 0) {
retval = check_link_count (file, log);
unlink (file);
return retval;
}
fd = open (lock, O_RDWR);
if (-1 == fd) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: %s: %s\n",
shadow_progname, lock, strerror (errno));
}
unlink (file);
errno = EINVAL;
return 0;
}
len = read (fd, buf, sizeof (buf) - 1);
close (fd);
if (len <= 0) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: existing lock file %s without a PID\n",
shadow_progname, lock);
}
unlink (file);
errno = EINVAL;
return 0;
}
buf[len] = '\0';
if (get_pid (buf, &pid) == 0) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: existing lock file %s with an invalid PID '%s'\n",
shadow_progname, lock, buf);
}
unlink (file);
errno = EINVAL;
return 0;
}
if (kill (pid, 0) == 0) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: lock %s already used by PID %lu\n",
shadow_progname, lock, (unsigned long) pid);
}
unlink (file);
errno = EEXIST;
return 0;
}
if (unlink (lock) != 0) {
if (log) {
(void) fprintf (shadow_logfd,
"%s: cannot get lock %s: %s\n",
shadow_progname, lock, strerror (errno));
}
unlink (file);
return 0;
}
retval = 0;
if (link (file, lock) == 0) {
retval = check_link_count (file, log);
} else {
if (log) {
(void) fprintf (shadow_logfd,
"%s: cannot get lock %s: %s\n",
shadow_progname, lock, strerror (errno));
}
}
unlink (file);
return retval;
}
static /*@null@*/ /*@dependent@*/FILE *fopen_set_perms (
const char *name,
@ -205,43 +351,38 @@ bool commonio_present (const struct commonio_db *db)
}
int do_fcntl_lock (const char *file, bool log, short type)
{
int fd;
struct flock lck = {
.l_type = type,
.l_whence = SEEK_SET,
.l_start = 0,
.l_len = 0,
};
fd = open (file, O_WRONLY | O_CREAT, 0600);
if (-1 == fd) {
if (log) {
(void) fprintf (shadow_logfd, "%s: %s: %s\n",
shadow_progname, file, strerror (errno));
}
return 0;
}
fcntl (fd, F_SETLKW, &lck);
return(1);
}
int commonio_lock_nowait (struct commonio_db *db, bool log)
{
char* file = NULL;
char* lock = NULL;
size_t lock_file_len;
size_t file_len;
int err = 0;
if (db->locked) {
return 1;
}
if (do_fcntl_lock (db->filename, log, F_WRLCK | F_RDLCK) != 0) {
file_len = strlen(db->filename) + 11;/* %lu max size */
lock_file_len = strlen(db->filename) + 6; /* sizeof ".lock" */
file = MALLOCARRAY(file_len, char);
if (file == NULL) {
goto cleanup_ENOMEM;
}
lock = MALLOCARRAY(lock_file_len, char);
if (lock == NULL) {
goto cleanup_ENOMEM;
}
snprintf (file, file_len, "%s.%lu",
db->filename, (unsigned long) getpid ());
snprintf (lock, lock_file_len, "%s.lock", db->filename);
if (do_lock_file (file, lock, log) != 0) {
db->locked = true;
lock_count++;
err = 1;
}
cleanup_ENOMEM:
free(file);
free(lock);
return err;
}
@ -332,6 +473,8 @@ static void dec_lock_count (void)
int commonio_unlock (struct commonio_db *db)
{
char lock[1024];
if (db->isopen) {
db->readonly = true;
if (commonio_close (db) == 0) {
@ -342,9 +485,13 @@ int commonio_unlock (struct commonio_db *db)
}
}
if (db->locked) {
/*
* Unlock in reverse order: remove the lock file,
* then call ulckpwdf() (if used) on last unlock.
*/
db->locked = false;
do_fcntl_lock (db->filename, false, F_UNLCK);
snprintf (lock, sizeof lock, "%s.lock", db->filename);
unlink (lock);
dec_lock_count ();
return 1;
}