From: Jia-Ju Bai Date: Wed, 24 Jul 2019 02:22:42 +0000 (+0800) Subject: fs: kernfs: Fix possible null-pointer dereferences in kernfs_path_from_node_locked() X-Git-Tag: v5.4-rc1~137^2~48 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=bbe70e4e421116db0af3acf84cbce3c3f6cac53e;p=linux.git 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 Link: https://lore.kernel.org/r/20190724022242.27505-1-baijiaju1990@gmail.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index ddf537923a0a..6ebae6bbe6a5 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -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,