[RFC PATCH ghak21 4/4] audit: add parent of refused symlink to audit_names

[Richard Guy Briggs <rgb@redhat.com>]

Audit link denied events for symlinks were missing the parent PATH
record.  Add it.  Since the full pathname may not be available,
reconstruct it from the path in the nameidata supplied.

See: https://github.com/linux-audit/audit-kernel/issues/21
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
 fs/namei.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/namei.c b/fs/namei.c
index 0edf133..bf1c046b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -923,6 +923,7 @@ static inline int may_follow_link(struct nameidata *nd)
 	const struct inode *inode;
 	const struct inode *parent;
 	kuid_t puid;
+	char *pathname;
 
 	if (!sysctl_protected_symlinks)
 		return 0;
@@ -945,6 +946,14 @@ static inline int may_follow_link(struct nameidata *nd)
 	if (nd->flags & LOOKUP_RCU)
 		return -ECHILD;
 
+	pathname = kmalloc(PATH_MAX + 1, GFP_KERNEL);
+	if (!pathname)
+		return -ENOMEM;
+	audit_inode(getname_kernel(d_absolute_path(&nd->stack[0].link, pathname,
+						   PATH_MAX + 1)),
+		    nd->stack[0].link.dentry, 0);
+	audit_inode(nd->name, nd->stack[0].link.dentry->d_parent, LOOKUP_PARENT);
+
 	audit_inode(nd->name, nd->stack[0].link.dentry, 0);
 	audit_log_link_denied("follow_link", &nd->stack[0].link);
 	return -EACCES;
-- 
1.8.3.1