audit: Report suspicious O_CREAT usage

This renames the very specific audit_log_link_denied() to
audit_log_path_denied() and adds the AUDIT_* type as an argument. This
allows for the creation of the new AUDIT_ANOM_CREAT that can be used to
report the fifo/regular file creation restrictions that were introduced
in commit 30aba6656f61 ("namei: allow restricted O_CREAT of FIFOs and
regular files").

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
diff --git a/fs/namei.c b/fs/namei.c
index 671c3c1..2dda552 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -925,7 +925,7 @@ static inline int may_follow_link(struct nameidata *nd)
 		return -ECHILD;
 
 	audit_inode(nd->name, nd->stack[0].link.dentry, 0);
-	audit_log_link_denied("follow_link");
+	audit_log_path_denied(AUDIT_ANOM_LINK, "follow_link");
 	return -EACCES;
 }
 
@@ -993,7 +993,7 @@ static int may_linkat(struct path *link)
 	if (safe_hardlink_source(inode) || inode_owner_or_capable(inode))
 		return 0;
 
-	audit_log_link_denied("linkat");
+	audit_log_path_denied(AUDIT_ANOM_LINK, "linkat");
 	return -EPERM;
 }
 
@@ -1031,6 +1031,10 @@ static int may_create_in_sticky(struct dentry * const dir,
 	    (dir->d_inode->i_mode & 0020 &&
 	     ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
 	      (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
+		const char *operation = S_ISFIFO(inode->i_mode) ?
+					"sticky_create_fifo" :
+					"sticky_create_regular";
+		audit_log_path_denied(AUDIT_ANOM_CREAT, operation);
 		return -EACCES;
 	}
 	return 0;