[PATCH] devfs: Do not create overlapping partitions

[Sascha Hauer]

Until now it has been possible to create overlapping partitions. Go away
from that and allow to create partitions only in unallocated areas of a
device. This lowers the risk of having inconsistent partitioning and
increases the chance that inconsistent partitioning is recognized by
the user.

We had explicit overlap checking for the environment partition which
becomes unnecessary with this change and is removed.

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 common/startup.c | 70 +-----------------------------------------------
 fs/devfs-core.c  | 34 +++++++++++++++++++++++
 2 files changed, 35 insertions(+), 69 deletions(-)

diff --git a/common/startup.c b/common/startup.c
index f72902fc53..f53b73f81a 100644
--- a/common/startup.c
+++ b/common/startup.c
@@ -68,70 +68,6 @@ static int mount_root(void)
 fs_initcall(mount_root);
 #endif
 
-#ifdef CONFIG_ENV_HANDLING
-static bool region_overlap(loff_t starta, loff_t lena,
-			   loff_t startb, loff_t lenb)
-{
-	if (starta + lena <= startb)
-		return 0;
-	if (startb + lenb <= starta)
-		return 0;
-	return 1;
-}
-
-static int check_overlap(const char *path)
-{
-	struct cdev *cenv, *cdisk, *cpart;
-	const char *name;
-
-	name = devpath_to_name(path);
-
-	if (name == path)
-		/*
-		 * no /dev/ in front, so *path is some file. No need to
-		 * check further.
-		 */
-		return 0;
-
-	cenv = cdev_by_name(name);
-	if (!cenv)
-		return -EINVAL;
-
-	if (cenv->mtd)
-		return 0;
-
-	cdisk = cenv->master;
-
-	if (!cdisk)
-		return 0;
-
-	list_for_each_entry(cpart, &cdisk->partitions, partition_entry) {
-		if (cpart == cenv)
-			continue;
-
-		if (region_overlap(cpart->offset, cpart->size,
-				   cenv->offset, cenv->size))
-			goto conflict;
-	}
-
-	return 0;
-
-conflict:
-	pr_err("Environment partition (0x%08llx-0x%08llx) "
-		"overlaps with partition %s (0x%08llx-0x%08llx), not using it\n",
-		cenv->offset, cenv->offset + cenv->size - 1,
-		cpart->name,
-		cpart->offset, cpart->offset + cpart->size - 1);
-
-	return -EINVAL;
-}
-#else
-static int check_overlap(const char *path)
-{
-	return 0;
-}
-#endif
-
 static int load_environment(void)
 {
 	const char *default_environment_path;
@@ -143,11 +79,7 @@ static int load_environment(void)
 		defaultenv_load("/env", 0);
 
 	if (IS_ENABLED(CONFIG_ENV_HANDLING)) {
-		ret = check_overlap(default_environment_path);
-		if (ret)
-			default_environment_path_set(NULL);
-		else
-			envfs_load(default_environment_path, "/env", 0);
+		envfs_load(default_environment_path, "/env", 0);
 	} else {
 		if (IS_ENABLED(CONFIG_DEFAULT_ENVIRONMENT))
 			pr_notice("No support for persistent environment. Using default environment\n");
diff --git a/fs/devfs-core.c b/fs/devfs-core.c
index 30ad0e0508..3715e543e6 100644
--- a/fs/devfs-core.c
+++ b/fs/devfs-core.c
@@ -301,6 +301,37 @@ int devfs_remove(struct cdev *cdev)
 	return 0;
 }
 
+static bool region_overlap(loff_t starta, loff_t lena,
+			   loff_t startb, loff_t lenb)
+{
+	if (starta + lena <= startb)
+		return 0;
+	if (startb + lenb <= starta)
+		return 0;
+	return 1;
+}
+
+static int check_overlap(struct cdev *cdev, const char *name, loff_t offset, loff_t size)
+{
+	struct cdev *cpart;
+
+	list_for_each_entry(cpart, &cdev->partitions, partition_entry) {
+		if (region_overlap(cpart->offset, cpart->size,
+				   offset, size))
+			goto conflict;
+	}
+
+	return 0;
+
+conflict:
+	pr_err("New partition %s (0x%08llx-0x%08llx) on %s "
+		"overlaps with partition %s (0x%08llx-0x%08llx), not creating it\n",
+		name, offset, offset + size - 1, cpart->name,
+		cpart->name, cpart->offset, cpart->offset + cpart->size - 1);
+
+	return -EINVAL;
+}
+
 static struct cdev *__devfs_add_partition(struct cdev *cdev,
 		const struct devfs_partition *partinfo, loff_t *end)
 {
@@ -336,6 +367,9 @@ static struct cdev *__devfs_add_partition(struct cdev *cdev,
 		return ERR_PTR(-EINVAL);
 	}
 
+	if (check_overlap(cdev, partinfo->name, offset, size))
+		return ERR_PTR(-EINVAL);
+
 	if (IS_ENABLED(CONFIG_MTD) && cdev->mtd) {
 		struct mtd_info *mtd;
 
-- 
2.30.2