[PATCH v3 84/87] libmultipath: add consistency check for alias settings

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From: Martin Wilck <mwilck@xxxxxxxx>

A typo in a config file, assigning the same alias to multiple WWIDs,
can cause massive confusion and even data corruption. Check and
if possible fix the bindings file in such cases.

Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
 libmultipath/alias.c | 265 +++++++++++++++++++++++++++++++++++++++++++
 libmultipath/alias.h |   3 +
 multipath/main.c     |   3 +
 multipathd/main.c    |   3 +
 4 files changed, 274 insertions(+)

diff --git a/libmultipath/alias.c b/libmultipath/alias.c
index 0759c4e..df44bdc 100644
--- a/libmultipath/alias.c
+++ b/libmultipath/alias.c
@@ -4,6 +4,7 @@
  */
 #include <stdlib.h>
 #include <errno.h>
+#include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
 #include <limits.h>
@@ -17,6 +18,9 @@
 #include "vector.h"
 #include "checkers.h"
 #include "structs.h"
+#include "config.h"
+#include "util.h"
+#include "errno.h"
 
 
 /*
@@ -438,3 +442,264 @@ get_user_friendly_wwid(const char *alias, char *buff, const char *file)
 	fclose(f);
 	return 0;
 }
+
+struct binding {
+	char *alias;
+	char *wwid;
+};
+
+static void _free_binding(struct binding *bdg)
+{
+	free(bdg->wwid);
+	free(bdg->alias);
+	free(bdg);
+}
+
+/*
+ * Perhaps one day we'll implement this more efficiently, thus use
+ * an abstract type.
+ */
+typedef struct _vector Bindings;
+
+static void free_bindings(Bindings *bindings)
+{
+	struct binding *bdg;
+	int i;
+
+	vector_foreach_slot(bindings, bdg, i)
+		_free_binding(bdg);
+	vector_reset(bindings);
+}
+
+enum {
+	BINDING_EXISTS,
+	BINDING_CONFLICT,
+	BINDING_ADDED,
+	BINDING_DELETED,
+	BINDING_NOTFOUND,
+	BINDING_ERROR,
+};
+
+static int add_binding(Bindings *bindings, const char *alias, const char *wwid)
+{
+	struct binding *bdg;
+	int i, cmp = 0;
+
+	/*
+	 * Keep the bindings array sorted by alias.
+	 * Optimization: Search backwards, assuming that the bindings file is
+	 * sorted already.
+	 */
+	vector_foreach_slot_backwards(bindings, bdg, i) {
+		if ((cmp = strcmp(bdg->alias, alias)) <= 0)
+			break;
+	}
+
+	/* Check for exact match */
+	if (i >= 0 && cmp == 0)
+		return strcmp(bdg->wwid, wwid) ?
+			BINDING_CONFLICT : BINDING_EXISTS;
+
+	i++;
+	bdg = calloc(1, sizeof(*bdg));
+	if (bdg) {
+		bdg->wwid = strdup(wwid);
+		bdg->alias = strdup(alias);
+		if (bdg->wwid && bdg->alias &&
+		    vector_insert_slot(bindings, i, bdg))
+			return BINDING_ADDED;
+		else
+			_free_binding(bdg);
+	}
+
+	return BINDING_ERROR;
+}
+
+static int write_bindings_file(const Bindings *bindings, int fd)
+{
+	struct binding *bnd;
+	char line[LINE_MAX];
+	int i;
+
+	if (write(fd, BINDINGS_FILE_HEADER, sizeof(BINDINGS_FILE_HEADER) - 1)
+	    != sizeof(BINDINGS_FILE_HEADER) - 1)
+		return -1;
+
+	vector_foreach_slot(bindings, bnd, i) {
+		int len;
+
+		len = snprintf(line, sizeof(line), "%s %s\n",
+			       bnd->alias, bnd->wwid);
+
+		if (len < 0 || (size_t)len >= sizeof(line)) {
+			condlog(1, "%s: line overflow", __func__);
+			return -1;
+		}
+
+		if (write(fd, line, len) != len)
+			return -1;
+	}
+	return 0;
+}
+
+static int fix_bindings_file(const struct config *conf,
+			     const Bindings *bindings)
+{
+	int rc;
+	long fd;
+	char tempname[PATH_MAX];
+
+	if (safe_sprintf(tempname, "%s.XXXXXX", conf->bindings_file))
+		return -1;
+	if ((fd = mkstemp(tempname)) == -1) {
+		condlog(1, "%s: mkstemp: %m", __func__);
+		return -1;
+	}
+	pthread_cleanup_push(close_fd, (void*)fd);
+	rc = write_bindings_file(bindings, fd);
+	pthread_cleanup_pop(1);
+	if (rc == -1) {
+		condlog(1, "failed to write new bindings file %s",
+			tempname);
+		unlink(tempname);
+		return rc;
+	}
+	if ((rc = rename(tempname, conf->bindings_file)) == -1)
+		condlog(0, "%s: rename: %m", __func__);
+	else
+		condlog(1, "updated bindings file %s", conf->bindings_file);
+	return rc;
+}
+
+static int _check_bindings_file(const struct config *conf, FILE *file,
+				 Bindings *bindings)
+{
+	int rc = 0;
+	unsigned int linenr = 0;
+	char *line = NULL;
+	size_t line_len = 0;
+	ssize_t n;
+
+	pthread_cleanup_push(free, line);
+	while ((n = getline(&line, &line_len, file)) >= 0) {
+		char *c, *alias, *wwid;
+		const char *mpe_wwid;
+
+		linenr++;
+		c = strpbrk(line, "#\n\r");
+		if (c)
+			*c = '\0';
+		alias = strtok(line, " \t");
+		if (!alias) /* blank line */
+			continue;
+		wwid = strtok(NULL, " \t");
+		if (!wwid) {
+			condlog(1, "invalid line %d in bindings file, missing WWID",
+				linenr);
+			continue;
+		}
+		c = strtok(NULL, " \t");
+		if (c)
+			/* This is non-fatal */
+			condlog(1, "invalid line %d in bindings file, extra args \"%s\"",
+				linenr, c);
+
+		mpe_wwid = get_mpe_wwid(conf->mptable, alias);
+		if (mpe_wwid && strcmp(mpe_wwid, wwid)) {
+			condlog(0, "ERROR: alias \"%s\" for WWID %s in bindings file "
+				"on line %u conflicts with multipath.conf entry for %s",
+				alias, wwid, linenr, mpe_wwid);
+			rc = -1;
+			continue;
+		}
+
+		switch (add_binding(bindings, alias, wwid)) {
+		case BINDING_CONFLICT:
+			condlog(0, "ERROR: multiple bindings for alias \"%s\" in "
+				"bindings file on line %u, discarding binding to WWID %s",
+				alias, linenr, wwid);
+			rc = -1;
+			break;
+		case BINDING_EXISTS:
+			condlog(2, "duplicate line for alias %s in bindings file on line %u",
+				alias, linenr);
+			break;
+		case BINDING_ERROR:
+			condlog(2, "error adding binding %s -> %s",
+				alias, wwid);
+			break;
+		default:
+			break;
+		}
+	}
+	pthread_cleanup_pop(1);
+	return rc;
+}
+
+static void cleanup_fclose(void *p)
+{
+	fclose(p);
+}
+
+/*
+ * check_alias_settings(): test for inconsistent alias configuration
+ *
+ * It's a fatal configuration error if the same alias is assigned to
+ * multiple WWIDs. In the worst case, it can cause data corruption
+ * by mangling devices with different WWIDs into the same multipath map.
+ * This function tests the configuration from multipath.conf and the
+ * bindings file for consistency, drops inconsistent multipath.conf
+ * alias settings, and rewrites the bindings file if necessary, dropping
+ * conflicting lines (if user_friendly_names is on, multipathd will
+ * fill in the deleted lines with a newly generated alias later).
+ * Note that multipath.conf is not rewritten. Use "multipath -T" for that.
+ *
+ * Returns: 0 in case of success, -1 if the configuration was bad
+ * and couldn't be fixed.
+ */
+int check_alias_settings(const struct config *conf)
+{
+	int can_write;
+	int rc = 0, i, fd;
+	Bindings bindings = {.allocated = 0, };
+	struct mpentry *mpe;
+
+	pthread_cleanup_push_cast(free_bindings, &bindings);
+	vector_foreach_slot(conf->mptable, mpe, i) {
+		if (!mpe->wwid || !mpe->alias)
+			continue;
+		if (add_binding(&bindings, mpe->alias, mpe->wwid) ==
+		    BINDING_CONFLICT) {
+			condlog(0, "ERROR: alias \"%s\" bound to multiple wwids in multipath.conf, "
+				"discarding binding to %s",
+				mpe->alias, mpe->wwid);
+			free(mpe->alias);
+			mpe->alias = NULL;
+		}
+	}
+	/* This clears the bindings */
+	pthread_cleanup_pop(1);
+
+	pthread_cleanup_push_cast(free_bindings, &bindings);
+	fd = open_file(conf->bindings_file, &can_write, BINDINGS_FILE_HEADER);
+	if (fd != -1) {
+		FILE *file = fdopen(fd, "r");
+
+		if (file != NULL) {
+			pthread_cleanup_push(cleanup_fclose, file);
+			rc = _check_bindings_file(conf, file, &bindings);
+			pthread_cleanup_pop(1);
+			if (rc == -1 && can_write && !conf->bindings_read_only)
+				rc = fix_bindings_file(conf, &bindings);
+			else if (rc == -1)
+				condlog(0, "ERROR: bad settings in read-only bindings file %s",
+					conf->bindings_file);
+		} else {
+			condlog(1, "failed to fdopen %s: %m",
+				conf->bindings_file);
+			close(fd);
+		}
+	}
+	pthread_cleanup_pop(1);
+	return rc;
+}
diff --git a/libmultipath/alias.h b/libmultipath/alias.h
index 236b3ba..dbc950c 100644
--- a/libmultipath/alias.h
+++ b/libmultipath/alias.h
@@ -10,4 +10,7 @@ char *use_existing_alias (const char *wwid, const char *file,
 			  const char *alias_old,
 			  const char *prefix, int bindings_read_only);
 
+struct config;
+int check_alias_settings(const struct config *);
+
 #endif /* _ALIAS_H */
diff --git a/multipath/main.c b/multipath/main.c
index 9e65070..80bc4b5 100644
--- a/multipath/main.c
+++ b/multipath/main.c
@@ -64,6 +64,7 @@
 #include "time-util.h"
 #include "file.h"
 #include "valid.h"
+#include "alias.h"
 
 int logsink;
 struct udev *udev;
@@ -958,6 +959,8 @@ main (int argc, char *argv[])
 		exit(RTVL_FAIL);
 	}
 
+	check_alias_settings(conf);
+
 	if (optind < argc) {
 		dev = MALLOC(FILE_NAME_SIZE);
 
diff --git a/multipathd/main.c b/multipathd/main.c
index 343ee95..9f12a57 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -63,6 +63,7 @@
 #include "uevent.h"
 #include "log.h"
 #include "uxsock.h"
+#include "alias.h"
 
 #include "mpath_cmd.h"
 #include "mpath_persist.h"
@@ -2717,6 +2718,8 @@ reconfigure (struct vectors * vecs)
 		conf->verbosity = verbosity;
 	if (bindings_read_only)
 		conf->bindings_read_only = bindings_read_only;
+	check_alias_settings(conf);
+
 	uxsock_timeout = conf->uxsock_timeout;
 
 	old = rcu_dereference(multipath_conf);
-- 
2.28.0


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