Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754861AbbGJOLH (ORCPT ); Fri, 10 Jul 2015 10:11:07 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:43024 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754455AbbGJOK7 (ORCPT ); Fri, 10 Jul 2015 10:10:59 -0400 From: Stefan Bader To: Kent Overstreet , linux-bcache@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@lists.ubuntu.com Subject: [PATCH resend] bcache: prevent crash on changing writeback_running Date: Fri, 10 Jul 2015 16:10:56 +0200 Message-Id: <1436537456-17338-1-git-send-email-stefan.bader@canonical.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1910 Lines: 52 I sent this out quite a while ago. Back then it was said that it was applied to the development tree. But it seems it never made its way upstream. I re-tested with a 4.0.7 kernel and compared this against a 4.0 kernel with this patch applied. Still it is possible to trigger a NULL pointer violation when writing 0 into writeback_running of a bcache device that is not attached to a cache set (without the patch). -Stefan --- >From e949c64fa6acbdaab999410250855a6a4fc6bad1 Mon Sep 17 00:00:00 2001 From: Stefan Bader Date: Mon, 18 Aug 2014 20:00:13 +0200 Subject: [PATCH] bcache: prevent crash on changing writeback_running commit a664d0f05a2e ("bcache: fix crash on shutdown in passthrough mode") added a safeguard in the shutdown case. At least while not being attached it is also possible to trigger a kernel bug by writing into writeback_running. This change adds the same check before trying to wake up the thread for that case. Signed-off-by: Stefan Bader --- drivers/md/bcache/writeback.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h index 0a9dab1..073a042 100644 --- a/drivers/md/bcache/writeback.h +++ b/drivers/md/bcache/writeback.h @@ -63,7 +63,8 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio, static inline void bch_writeback_queue(struct cached_dev *dc) { - wake_up_process(dc->writeback_thread); + if (!IS_ERR_OR_NULL(dc->writeback_thread)) + wake_up_process(dc->writeback_thread); } static inline void bch_writeback_add(struct cached_dev *dc) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/