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fs: kernfs: Fix possible null-pointer dereferences in kernfs_path_from_node_locked()

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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>
This commit is contained in:
Jia-Ju Bai 2019-07-24 10:22:42 +08:00 committed by Greg Kroah-Hartman
parent 2fd60da46d
commit bbe70e4e42
1 changed files with 4 additions and 2 deletions
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6
fs/kernfs/dir.c
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@ -137,6 +137,9 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
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 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
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,