From: John Snow <jsnow@redhat.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
qemu-devel@nongnu.org, qemu-block@nongnu.org
Cc: kwolf@redhat.com, famz@redhat.com, mreitz@redhat.com,
stefanha@redhat.com, den@openvz.org
Subject: Re: [Qemu-devel] [Qemu-block] [PATCH 1/3] blockjob: fix dead pointer in txn list
Date: Mon, 1 Aug 2016 18:39:28 -0400 [thread overview]
Message-ID: <9586a77d-3656-94e9-b94c-edb45ea10816@redhat.com> (raw)
In-Reply-To: <1469616590-38683-2-git-send-email-vsementsov@virtuozzo.com>
On 07/27/2016 06:49 AM, Vladimir Sementsov-Ogievskiy wrote:
> Job may be freed in block_job_unref and in this case this would break
> transaction QLIST.
>
> Fix this by removing job from this list before unref.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> blockjob.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/blockjob.c b/blockjob.c
> index a5ba3be..e045091 100644
> --- a/blockjob.c
> +++ b/blockjob.c
> @@ -216,6 +216,7 @@ static void block_job_completed_single(BlockJob *job)
> }
> job->cb(job->opaque, job->ret);
> if (job->txn) {
> + QLIST_REMOVE(job, txn_list);
> block_job_txn_unref(job->txn);
> }
> block_job_unref(job);
>
Has this caused actual problems for you?
This function is only ever called in a transactional context if the
transaction is over -- so we're not likely to use the pointers ever
again anyway.
Still, it's good practice, and the caller uses a safe iteration of the
list, so I think this should be safe.
But I don't think this SHOULD fix an actual bug. If it does, I think
something else is wrong.
Tested-by: John Snow <jsnow@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
next prev parent reply other threads:[~2016-08-01 22:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-27 10:49 [Qemu-devel] [PATCH RFC 0/3] Backup/blockjob fixes Vladimir Sementsov-Ogievskiy
2016-07-27 10:49 ` [Qemu-devel] [PATCH 1/3] blockjob: fix dead pointer in txn list Vladimir Sementsov-Ogievskiy
2016-08-01 22:39 ` John Snow [this message]
2016-08-02 11:05 ` [Qemu-devel] [Qemu-block] " Vladimir Sementsov-Ogievskiy
2016-08-02 16:50 ` John Snow
2016-07-27 10:49 ` [Qemu-devel] [PATCH 2/3] backup: fix transaction fail scenario Vladimir Sementsov-Ogievskiy
2016-07-27 10:49 ` [Qemu-devel] [PATCH 3/3] blockjob: fix transaction cancel Vladimir Sementsov-Ogievskiy
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