fs: add link restriction audit reporting

Adds audit messages for unexpected link restriction violations so that
system owners will have some sort of potentially actionable information
about misbehaving processes.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 21 insertions, 0 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index 1c7f2c61416b..fda8bd9e1d3a 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1450,6 +1450,27 @@ void audit_log_key(struct audit_buffer *ab, char *key)
 }
 
 /**
+ * audit_log_link_denied - report a link restriction denial
+ * @operation: specific link opreation
+ * @link: the path that triggered the restriction
+ */
+void audit_log_link_denied(const char *operation, struct path *link)
+{
+        struct audit_buffer *ab;
+
+        ab = audit_log_start(current->audit_context, GFP_KERNEL,
+                             AUDIT_ANOM_LINK);
+        audit_log_format(ab, "op=%s action=denied", operation);
+        audit_log_format(ab, " pid=%d comm=", current->pid);
+        audit_log_untrustedstring(ab, current->comm);
+        audit_log_d_path(ab, " path=", link);
+        audit_log_format(ab, " dev=");
+        audit_log_untrustedstring(ab, link->dentry->d_inode->i_sb->s_id);
+        audit_log_format(ab, " ino=%lu", link->dentry->d_inode->i_ino);
+        audit_log_end(ab);
+}
+
+/**
  * audit_log_end - end one audit record
  * @ab: the audit_buffer
  *