From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752711AbbIGM03 (ORCPT ); Mon, 7 Sep 2015 08:26:29 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:37931 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750961AbbIGM0Y (ORCPT ); Mon, 7 Sep 2015 08:26:24 -0400 From: Dmitry Vyukov To: gregkh@linuxfoundation.org, peter@hurleysoftware.com, jslaby@suse.com, linux-kernel@vger.kernel.org Cc: jslaby@suse.cz, andreyknvl@google.com, kcc@google.com, glider@google.com, paulmck@linux.vnet.ibm.com, hboehm@google.com, Dmitry Vyukov Subject: [PATCH] tty: fix data race in tty_buffer_flush Date: Mon, 7 Sep 2015 14:26:21 +0200 Message-Id: <1441628781-73974-1-git-send-email-dvyukov@google.com> X-Mailer: git-send-email 2.5.0.457.gab17608 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org tty_buffer_flush frees not acquired buffers. As the result, for example, read of b->size in tty_buffer_free can return garbage value which will lead to a huge buffer hanging in the freelist. This is just the benignest manifestation of freeing of a not acquired object. If the object is passed to kfree, heap can be corrupted. Acquire visibility over the buffer before freeing it. The data race was found with KernelThreadSanitizer (KTSAN). Signed-off-by: Dmitry Vyukov --- drivers/tty/tty_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 5a3fa89..7dab1b3 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -242,7 +242,7 @@ void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld) atomic_inc(&buf->priority); mutex_lock(&buf->lock); - while ((next = buf->head->next) != NULL) { + while ((next = smp_load_acquire(&buf->head->next)) != NULL) { tty_buffer_free(port, buf->head); buf->head = next; } -- 2.5.0.457.gab17608