Make _init_rand() thread safe - use rand_r() instead of rand().

Use good entropy for seed value if possible.

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.02.44 - 
 ====================================
+  Use better random seed value in temp file creation.
   Add generic function to read /dev/urandom, used in uuid calculation.
   Use displayable_lvs_in_vg and lv_is_displayable for consistency throughout.
   Fix race in vgcreate that would result in second caller overwriting first.

lib/commands/toolcontext.c

@@ -979,6 +979,14 @@ static int _init_backup(struct cmd_context *cmd)
 	return 1;
 }
 
+static void _init_rand(struct cmd_context *cmd)
+{
+	if (read_urandom(&cmd->rand_seed, sizeof(cmd->rand_seed)))
+		return;
+
+	cmd->rand_seed = (unsigned) time(NULL) + (unsigned) getpid();
+}
+
 /* Entry point */
 struct cmd_context *create_toolcontext(struct arg *the_args, unsigned is_static,
 				       unsigned is_long_lived)
@@ -1077,6 +1085,8 @@ struct cmd_context *create_toolcontext(struct arg *the_args, unsigned is_static,
 	if (!_init_backup(cmd))
 		goto error;
 
+	_init_rand(cmd);
+
 	cmd->default_settings.cache_vgmetadata = 1;
 	cmd->current_settings = cmd->default_settings;
 

lib/commands/toolcontext.h

@@ -62,6 +62,7 @@ struct cmd_context {
 	const char *hostname;
 	const char *kernel_vsn;
 
+	unsigned rand_seed;
 	char *cmd_line;
 	struct command *command;
 	struct arg *args;

lib/format_text/archive.c

@@ -236,7 +236,8 @@ int archive_vg(struct volume_group *vg,
 	/*
 	 * Write the vg out to a temporary file.
 	 */
-	if (!create_temp_name(dir, temp_file, sizeof(temp_file), &fd)) {
+	if (!create_temp_name(dir, temp_file, sizeof(temp_file), &fd,
+			      &vg->cmd->rand_seed)) {
 		log_err("Couldn't create temporary archive name.");
 		return 0;
 	}

lib/format_text/format-text.c

@@ -848,7 +848,8 @@ static int _vg_write_file(struct format_instance *fid __attribute((unused)),
 		return 0;
 	}
 
-	if (!create_temp_name(temp_dir, temp_file, sizeof(temp_file), &fd)) {
+	if (!create_temp_name(temp_dir, temp_file, sizeof(temp_file), &fd,
+			      &vg->cmd->rand_seed)) {
 		log_err("Couldn't create temporary text file name.");
 		return 0;
 	}

lib/misc/lvm-file.c

@@ -29,7 +29,8 @@
  * rename the file after successfully writing it.  Grab
  * NFS-supported exclusive fcntl discretionary lock.
  */
-int create_temp_name(const char *dir, char *buffer, size_t len, int *fd)
+int create_temp_name(const char *dir, char *buffer, size_t len, int *fd,
+		     unsigned *seed)
 {
 	int i, num;
 	pid_t pid;
@@ -41,7 +42,7 @@ int create_temp_name(const char *dir, char *buffer, size_t len, int *fd)
 		.l_len = 0
 	};
 
-	num = rand();
+	num = rand_r(seed);
 	pid = getpid();
 	if (gethostname(hostname, sizeof(hostname)) < 0) {
 		log_sys_error("gethostname", "");

lib/misc/lvm-file.h

@@ -19,7 +19,8 @@
 /*
  * Create a temporary filename, and opens a descriptor to the file.
  */
-int create_temp_name(const char *dir, char *buffer, size_t len, int *fd);
+int create_temp_name(const char *dir, char *buffer, size_t len, int *fd,
+		     unsigned *seed);
 
 /*
  * NFS-safe rename of a temporary file to a common name, designed

tools/lvmcmdline.c

@@ -997,11 +997,6 @@ int lvm_split(char *str, int *argc, char **argv, int max)
 	return *argc;
 }
 
-static void _init_rand(void)
-{
-	srand((unsigned) time(NULL) + (unsigned) getpid());
-}
-
 static const char *_get_cmdline(pid_t pid)
 {
 	static char _proc_cmdline[32];
@@ -1096,8 +1091,6 @@ struct cmd_context *init_lvm(unsigned is_static)
 	if (!(cmd = create_toolcontext(_cmdline.the_args, is_static, 0)))
 		return_NULL;
 
-	_init_rand();
-
 	_apply_settings(cmd);
 
 	return cmd;