Merge tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull hostfs fix from Al Viro:
 "Fix hostfs __dentry_name() string handling.

  The use of strcpy() with overlapping source and destination is a UB;
  original loop hadn't been. More to the point, the whole thing is much
  easier done with memcpy() + memmove()"

* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  hostfs: fix string handling in __dentry_name()

1 files changed, 6 insertions, 21 deletions

diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index 844c45253452..e0741e468956 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -95,32 +95,17 @@ __uml_setup("hostfs=", hostfs_args,
 static char *__dentry_name(struct dentry *dentry, char *name)
 {
 	char *p = dentry_path_raw(dentry, name, PATH_MAX);
-	char *root;
-	size_t len;
-	struct hostfs_fs_info *fsi;
-
-	fsi = dentry->d_sb->s_fs_info;
-	root = fsi->host_root_path;
-	len = strlen(root);
-	if (IS_ERR(p)) {
-		__putname(name);
-		return NULL;
-	}
-
-	/*
-	 * This function relies on the fact that dentry_path_raw() will place
-	 * the path name at the end of the provided buffer.
-	 */
-	BUG_ON(p + strlen(p) + 1 != name + PATH_MAX);
+	struct hostfs_fs_info *fsi = dentry->d_sb->s_fs_info;
+	char *root = fsi->host_root_path;
+	size_t len = strlen(root);
 
-	strscpy(name, root, PATH_MAX);
-	if (len > p - name) {
+	if (IS_ERR(p) || len > p - name) {
 		__putname(name);
 		return NULL;
 	}
 
-	if (p > name + len)
-		strcpy(name + len, p);
+	memcpy(name, root, len);
+	memmove(name + len, p, name + PATH_MAX - p);
 
 	return name;
 }