File shadow-4.8.1-lock-mechanism.patch of Package shadow
Based on:
https://github.com/shadow-maint/shadow/commit/65470e5c7ddbc2885ad35fbd0218b91a75626c2f
Index: shadow-4.8.1/lib/commonio.c
===================================================================
--- shadow-4.8.1.orig/lib/commonio.c
+++ shadow-4.8.1/lib/commonio.c
@@ -54,8 +54,6 @@
/* local function prototypes */
static int lrename (const char *, const char *);
-static int check_link_count (const char *file);
-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,
@@ -117,140 +115,6 @@ int lrename (const char *old, const char
return res;
}
-static int check_link_count (const char *file)
-{
- struct stat sb;
-
- if (stat (file, &sb) != 0) {
- return 0;
- }
-
- if (sb.st_nlink != 2) {
- 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 (stderr,
- "%s: %s: %s\n",
- Prog, 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 (stderr,
- "%s: %s: %s\n",
- Prog, file, strerror (errno));
- }
- (void) close (fd);
- unlink (file);
- return 0;
- }
- close (fd);
-
- if (link (file, lock) == 0) {
- retval = check_link_count (file);
- if ((0==retval) && log) {
- (void) fprintf (stderr,
- "%s: %s: lock file already used\n",
- Prog, file);
- }
- unlink (file);
- return retval;
- }
-
- fd = open (lock, O_RDWR);
- if (-1 == fd) {
- if (log) {
- (void) fprintf (stderr,
- "%s: %s: %s\n",
- Prog, 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 (stderr,
- "%s: existing lock file %s without a PID\n",
- Prog, lock);
- }
- unlink (file);
- errno = EINVAL;
- return 0;
- }
- buf[len] = '\0';
- if (get_pid (buf, &pid) == 0) {
- if (log) {
- (void) fprintf (stderr,
- "%s: existing lock file %s with an invalid PID '%s'\n",
- Prog, lock, buf);
- }
- unlink (file);
- errno = EINVAL;
- return 0;
- }
- if (kill (pid, 0) == 0) {
- if (log) {
- (void) fprintf (stderr,
- "%s: lock %s already used by PID %lu\n",
- Prog, lock, (unsigned long) pid);
- }
- unlink (file);
- errno = EEXIST;
- return 0;
- }
- if (unlink (lock) != 0) {
- if (log) {
- (void) fprintf (stderr,
- "%s: cannot get lock %s: %s\n",
- Prog, lock, strerror (errno));
- }
- unlink (file);
- return 0;
- }
-
- retval = 0;
- if (link (file, lock) == 0) {
- retval = check_link_count (file);
- if ((0==retval) && log) {
- (void) fprintf (stderr,
- "%s: %s: lock file already used\n",
- Prog, file);
- }
- } else {
- if (log) {
- (void) fprintf (stderr,
- "%s: cannot get lock %s: %s\n",
- Prog, lock, strerror (errno));
- }
- }
-
- unlink (file);
- return retval;
-}
-
static /*@null@*/ /*@dependent@*/FILE *fopen_set_perms (
const char *name,
@@ -374,6 +238,29 @@ bool commonio_present (const struct comm
return (access (db->filename, F_OK) == 0);
}
+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, 0600);
+ if (-1 == fd) {
+ if (log) {
+ (void) fprintf (stderr, "%s: %s: %s\n",
+ Prog, file, strerror (errno));
+ }
+ return 0;
+ }
+
+ fcntl (fd, F_OFD_SETLKW, &lck);
+ close(fd);
+ return(1);
+}
int commonio_lock_nowait (struct commonio_db *db, bool log)
{
@@ -398,8 +285,7 @@ int commonio_lock_nowait (struct commoni
}
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) {
+ if (do_fcntl_lock (db->filename, log, F_WRLCK | F_RDLCK) != 0) {
db->locked = true;
lock_count++;
err = 1;
@@ -499,8 +385,6 @@ 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) {
@@ -511,13 +395,8 @@ int commonio_unlock (struct commonio_db
}
}
if (db->locked) {
- /*
- * Unlock in reverse order: remove the lock file,
- * then call ulckpwdf() (if used) on last unlock.
- */
db->locked = false;
- snprintf (lock, sizeof lock, "%s.lock", db->filename);
- unlink (lock);
+ do_fcntl_lock (db->filename, false, F_UNLCK);
dec_lock_count ();
return 1;
}
Index: shadow-4.8.1/lib/commonio.h
===================================================================
--- shadow-4.8.1.orig/lib/commonio.h
+++ shadow-4.8.1/lib/commonio.h
@@ -150,6 +150,7 @@ extern int commonio_setname (struct comm
extern bool commonio_present (const struct commonio_db *db);
extern int commonio_lock (struct commonio_db *);
extern int commonio_lock_nowait (struct commonio_db *, bool log);
+extern int do_fcntl_lock (const char *file, bool log, short type);
extern int commonio_open (struct commonio_db *, int);
extern /*@observer@*/ /*@null@*/const void *commonio_locate (struct commonio_db *, const char *);
extern int commonio_update (struct commonio_db *, const void *);
