From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932525Ab2JAW7m (ORCPT ); Mon, 1 Oct 2012 18:59:42 -0400 Received: from 1wt.eu ([62.212.114.60]:34991 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932474Ab2JAW7k (ORCPT ); Mon, 1 Oct 2012 18:59:40 -0400 Message-Id: <20121001225158.844516867@1wt.eu> User-Agent: quilt/0.48-1 Date: Tue, 02 Oct 2012 00:52:26 +0200 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Xiaotian Feng , Greg Kroah-Hartman , Willy Tarreau Subject: [ 029/180] tty_audit: fix tty_audit_add_data live lock on audit disabled In-Reply-To: <6a854f579a99b4fe2efaca1057e8ae22@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Xiaotian Feng commit 00bff392c81e4fb1901e5160fdd5afdb2546a6ab upstream. The current tty_audit_add_data code: do { size_t run; run = N_TTY_BUF_SIZE - buf->valid; if (run > size) run = size; memcpy(buf->data + buf->valid, data, run); buf->valid += run; data += run; size -= run; if (buf->valid == N_TTY_BUF_SIZE) tty_audit_buf_push_current(buf); } while (size != 0); If the current buffer is full, kernel will then call tty_audit_buf_push_current to empty the buffer. But if we disabled audit at the same time, tty_audit_buf_push() returns immediately if audit_enabled is zero. Without emptying the buffer. With obvious effect on tty_audit_add_data() that ends up spinning in that loop, copying 0 bytes at each iteration and attempting to push each time without any effect. Holding the lock all along. Suggested-by: Alexander Viro Signed-off-by: Xiaotian Feng Signed-off-by: Greg Kroah-Hartman Signed-off-by: Willy Tarreau --- drivers/char/tty_audit.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/drivers/char/tty_audit.c b/drivers/char/tty_audit.c index ac16fbe..dd4691a 100644 --- a/drivers/char/tty_audit.c +++ b/drivers/char/tty_audit.c @@ -94,8 +94,10 @@ static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid, { if (buf->valid == 0) return; - if (audit_enabled == 0) + if (audit_enabled == 0) { + buf->valid = 0; return; + } tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor, buf->data, buf->valid); buf->valid = 0; -- 1.7.2.1.45.g54fbc