libblkid: Add error checking to devicemapper code to avoid segfaults

If a device mapper volume disappears while libblkid code is running,
it is possible for the devicemapper code to return errors, and since
libblkid wasn't checking for error returns, it would dereference a
null pointer and crash.  Add error checking to prevent this.

Addresses-RedHat-Bugzilla: #433857

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 61 insertions, 44 deletions

diff --git a/lib/blkid/devname.c b/lib/blkid/devname.c
index fd646960..29cde8e7 100644
--- a/lib/blkid/devname.c
+++ b/lib/blkid/devname.c
@@ -154,8 +154,10 @@ set_pri:
 }
 
 #ifdef HAVE_DEVMAPPER
-static void dm_quiet_log(int level, const char *file, int line,
-			 const char *f, ...)
+static void dm_quiet_log(int level __BLKID_ATTR((unused)), 
+			 const char *file __BLKID_ATTR((unused)), 
+			 int line __BLKID_ATTR((unused)),
+			 const char *f __BLKID_ATTR((unused)), ...)
 {
 	return;
 }
@@ -168,38 +170,43 @@ static int dm_device_has_dep(const dev_t dev, const char *name)
 	struct dm_task *task;
 	struct dm_deps *deps;
 	struct dm_info info;
-	int i;
+	unsigned int i;
+	int ret = 0;
 
 	task = dm_task_create(DM_DEVICE_DEPS);
 	if (!task)
-		return 0;
+		goto out;
 
-	dm_task_set_name(task, name);
-	dm_task_run(task);
-	dm_task_get_info(task, &info);
+	if (!dm_task_set_name(task, name))
+		goto out;
 
-	if (!info.exists) {
-		dm_task_destroy(task);
-		return 0;
-	}
+	if (!dm_task_run(task))
+		goto out;
 
+	if (!dm_task_get_info(task, &info))
+		goto out;
+
+	if  (!info.exists)
+		goto out;
+  
 	deps = dm_task_get_deps(task);
-	if (!deps || deps->count == 0) {
-		dm_task_destroy(task);
-		return 0;
-	}
+	if (!deps || deps->count == 0)
+		goto out;
 
 	for (i = 0; i < deps->count; i++) {
 		dev_t dep_dev = deps->device[i];
 
 		if (dev == dep_dev) {
-			dm_task_destroy(task);
-			return 1;
+			ret = 1;
+			goto out;
 		}
 	}
 
-	dm_task_destroy(task);
-	return 0;
+out:
+	if (task)
+		dm_task_destroy(task);
+
+	return ret;
 }
 
 static int dm_device_is_leaf(const dev_t dev)
@@ -212,19 +219,20 @@ static int dm_device_is_leaf(const dev_t dev)
 	dm_log_init(dm_quiet_log);
 	task = dm_task_create(DM_DEVICE_LIST);
 	if (!task)
-		return 1;
+		goto out;
+
 	dm_log_init(0);
 
-	dm_task_run(task);
+	if (!dm_task_run(task))
+		goto out;
+
 	names = dm_task_get_names(task);
-	if (!names || !names->dev) {
-		dm_task_destroy(task);
-		return 1;
-	}
+	if (!names || !names->dev)
+		goto out;
 
 	n = 0;
 	do {
-		names = (void *)names + next;
+		names = (struct dm_names *) ((char *)names + next);
 
 		if (dm_device_has_dep(dev, names->name))
 			ret = 0;
@@ -232,7 +240,9 @@ static int dm_device_is_leaf(const dev_t dev)
 		next = names->next;
 	} while (next);
 
-	dm_task_destroy(task);
+out:
+	if (task)
+		dm_task_destroy(task);
 
 	return ret;
 }
@@ -245,20 +255,25 @@ static dev_t dm_get_devno(const char *name)
 
 	task = dm_task_create(DM_DEVICE_INFO);
 	if (!task)
-		return ret;
+		goto out;
 
-	dm_task_set_name(task, name);
-	dm_task_run(task);
-	dm_task_get_info(task, &info);
+	if (!dm_task_set_name(task, name))
+		goto out;
 
-	if (!info.exists) {
-		dm_task_destroy(task);
-		return ret;
-	}
+	if (!dm_task_run(task))
+		goto out;
+
+	if (!dm_task_get_info(task, &info))
+		goto out;
+
+	if (!info.exists)
+		goto out;
 
 	ret = makedev(info.major, info.minor);
 
-	dm_task_destroy(task);
+out:
+	if (task)
+		dm_task_destroy(task);
 	
 	return ret;
 }
@@ -273,15 +288,15 @@ static void dm_probe_all(blkid_cache cache, int only_if_new)
 	dm_log_init(dm_quiet_log);
 	task = dm_task_create(DM_DEVICE_LIST);
 	if (!task)
-		return;
+		goto out;
 	dm_log_init(0);
 
-	dm_task_run(task);
+	if (!dm_task_run(task))
+		goto out;
+
 	names = dm_task_get_names(task);
-	if (!names || !names->dev) {
-		dm_task_destroy(task);
-		return;
-	}
+	if (!names || !names->dev)
+		goto out;
 
 	n = 0;
 	do {
@@ -289,7 +304,7 @@ static void dm_probe_all(blkid_cache cache, int only_if_new)
 		char *device = NULL;
 		dev_t dev = 0;
 
-		names = (void *)names + next;
+		names = (struct dm_names *) ((char *)names + next);
 
 		rc = asprintf(&device, "mapper/%s", names->name);
 		if (rc < 0)
@@ -309,7 +324,9 @@ try_next:
 		next = names->next;
 	} while (next);
 
-	dm_task_destroy(task);
+out:
+	if (task)
+		dm_task_destroy(task);
 }
 #endif /* HAVE_DEVMAPPER */