From: Yiwen Jiang <jiangyiwen@huawei.com>
Date: Fri, 4 Sep 2015 22:44:37 +0000 (-0700)
Subject: ocfs2: avoid access invalid address when read o2dlm debug messages
X-Git-Tag: omap-for-v4.3/fixes-rc1~87^2~75
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f57a22ddecd6f26040a67e2c12880f98f88b6e00;p=pandora-kernel.git

ocfs2: avoid access invalid address when read o2dlm debug messages

The following case will lead to a lockres is freed but is still in use.

cat /sys/kernel/debug/o2dlm/locking_state	dlm_thread
lockres_seq_start
    -> lock dlm->track_lock
    -> get resA
                                                resA->refs decrease to 0,
                                                call dlm_lockres_release,
                                                and wait for "cat" unlock.
Although resA->refs is already set to 0,
increase resA->refs, and then unlock
                                                lock dlm->track_lock
                                                    -> list_del_init()
                                                    -> unlock
                                                    -> free resA

In such a race case, invalid address access may occurs.  So we should
delete list res->tracking before resA->refs decrease to 0.

Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
Reviewed-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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