fs: kernfs: Fix possible null-pointer dereferences in kernfs_path_from_node_locked()
In kernfs_path_from_node_locked(), there is an if statement on line 147
to check whether buf is NULL:
if (buf)
When buf is NULL, it is used on line 151:
len += strlcpy(buf + len, parent_str, ...)
and line 158:
len += strlcpy(buf + len, "/", ...)
and line 160:
len += strlcpy(buf + len, kn->name, ...)
Thus, possible null-pointer dereferences may occur.
To fix these possible bugs, buf is checked before being used.
If it is NULL, -EINVAL is returned.
These bugs are found by a static analysis tool STCheck written by us.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Link: https://lore.kernel.org/r/20190724022242.27505-1-baijiaju1990@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index ddf5379..6ebae6b 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -137,6 +137,9 @@
if (kn_from == kn_to)
return strlcpy(buf, "/", buflen);
+ if (!buf)
+ return -EINVAL;
+
common = kernfs_common_ancestor(kn_from, kn_to);
if (WARN_ON(!common))
return -EINVAL;
@@ -144,8 +147,7 @@
depth_to = kernfs_depth(common, kn_to);
depth_from = kernfs_depth(common, kn_from);
- if (buf)
- buf[0] = '\0';
+ buf[0] = '\0';
for (i = 0; i < depth_from; i++)
len += strlcpy(buf + len, parent_str,
