On Thu, Jan 29, 2015 at 2:28 AM, Bart Van Assche
<bart.vanass...@sandisk.com> wrote:
> This patch fixes a use-after-free that was introduced via patch
> "blk-mq: fix hctx/ctx kobject use-after-free" (commit
> 76d697d10769; kernel v3.19-rc4) and fixes the following crash:
Sorry, my fault, I shouldn't have linked mq's release with mq_kobj,
which may be released before running blk_cleanup_queue().
Another approach may be to revert the faulty commit and release all
mq stuff in request queue's release handler(blk_release_queue)
which should be more safe and simple.
>
> general protection fault: 0000 [#1] SMP
> Workqueue: srp_remove srp_remove_work [ib_srp]
> task: ffff88083530c880 ti: ffff880835774000 task.ti: ffff880835774000
> [<ffffffff8125a43c>] blk_mq_tag_wakeup_all+0x1c/0x90
> RDI: 6b6b6b6b6b6b6b6b
> Call Trace:
> [<ffffffff8125792e>] blk_mq_wake_waiters+0x4e/0x80
> [<ffffffff81247e86>] blk_set_queue_dying+0x26/0x90
> [<ffffffff8124abe5>] blk_cleanup_queue+0x35/0x250
> [<ffffffffa001ce4a>] __scsi_remove_device+0x5a/0xe0 [scsi_mod]
> [<ffffffffa001b48f>] scsi_forget_host+0x6f/0x80 [scsi_mod]
> [<ffffffffa000d646>] scsi_remove_host+0x86/0x140 [scsi_mod]
> [<ffffffffa0884c0b>] srp_remove_work+0x9b/0x210 [ib_srp]
> [<ffffffff8106ff48>] process_one_work+0x1d8/0x780
> [<ffffffff8107060b>] worker_thread+0x11b/0x460
> [<ffffffff81075c8f>] kthread+0xef/0x110
> [<ffffffff814dbdac>] ret_from_fork+0x7c/0xb0
>
> Signed-off-by: Bart Van Assche <bart.vanass...@sandisk.com>
> Cc: Ming Lei <ming....@canonical.com>
> Cc: Sasha Levin <sasha.le...@oracle.com>
> Cc: Christoph Hellwig <h...@lst.de>
> ---
> block/blk-mq-sysfs.c | 15 +++++----------
> block/blk-mq.c | 12 +++++++-----
> 2 files changed, 12 insertions(+), 15 deletions(-)
>
> diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
> index 6774a0e..921f7cf 100644
> --- a/block/blk-mq-sysfs.c
> +++ b/block/blk-mq-sysfs.c
> @@ -19,6 +19,8 @@ static void blk_mq_sysfs_release(struct kobject *kobj)
>
> q = container_of(kobj, struct request_queue, mq_kobj);
> free_percpu(q->queue_ctx);
> + kfree(q->queue_hw_ctx);
> + q->queue_hw_ctx = NULL;
> }
>
> static void blk_mq_ctx_release(struct kobject *kobj)
> @@ -34,6 +36,7 @@ static void blk_mq_hctx_release(struct kobject *kobj)
> struct blk_mq_hw_ctx *hctx;
>
> hctx = container_of(kobj, struct blk_mq_hw_ctx, kobj);
> + kfree(hctx->ctxs);
> kfree(hctx);
> }
>
> @@ -388,21 +391,13 @@ void blk_mq_unregister_disk(struct gendisk *disk)
> {
> struct request_queue *q = disk->queue;
> struct blk_mq_hw_ctx *hctx;
> - struct blk_mq_ctx *ctx;
> - int i, j;
> + int i;
>
> - queue_for_each_hw_ctx(q, hctx, i) {
> + queue_for_each_hw_ctx(q, hctx, i)
> blk_mq_unregister_hctx(hctx);
>
> - hctx_for_each_ctx(hctx, ctx, j)
> - kobject_put(&ctx->kobj);
> -
> - kobject_put(&hctx->kobj);
> - }
> -
> kobject_uevent(&q->mq_kobj, KOBJ_REMOVE);
> kobject_del(&q->mq_kobj);
> - kobject_put(&q->mq_kobj);
>
> kobject_put(&disk_to_dev(disk)->kobj);
> }
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 9ee3b87..6d007a4 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1604,7 +1604,8 @@ static void blk_mq_exit_hctx(struct request_queue *q,
> struct blk_mq_tag_set *set,
> struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
> {
> - unsigned flush_start_tag = set->queue_depth;
> + struct blk_mq_ctx *ctx;
> + unsigned j, flush_start_tag = set->queue_depth;
>
> blk_mq_tag_idle(hctx);
>
> @@ -1618,8 +1619,10 @@ static void blk_mq_exit_hctx(struct request_queue *q,
>
> blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
> blk_free_flush_queue(hctx->fq);
> - kfree(hctx->ctxs);
> blk_mq_free_bitmap(&hctx->ctx_map);
> + hctx_for_each_ctx(hctx, ctx, j)
> + kobject_put(&ctx->kobj);
> + kobject_put(&hctx->kobj);
> }
>
> static void blk_mq_exit_hw_queues(struct request_queue *q,
> @@ -2000,10 +2003,9 @@ void blk_mq_free_queue(struct request_queue *q)
>
> percpu_ref_exit(&q->mq_usage_counter);
>
> - kfree(q->queue_hw_ctx);
> - kfree(q->mq_map);
> + kobject_put(&q->mq_kobj);
>
> - q->queue_hw_ctx = NULL;
> + kfree(q->mq_map);
> q->mq_map = NULL;
>
> mutex_lock(&all_q_mutex);
> --
> 2.1.2
>
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