On 10/06/15 13:32, Junichi Nomura wrote:
> The commit 1bab0de0274f ("dm-mpath, scsi_dh: don't let dm detach device
> handlers") removed reference counting of attached scsi device handler.
> As a result, handler data is freed immediately via scsi_dh->detach()
> in the context of scsi_remove_device() where activation request can be
> still in flight.
>
> This patch moves scsi_dh_handler_detach() to sdev releasing function,
> scsi_device_dev_release_usercontext(), at that point the device
> is already in quiesced state.
>
> Fixes: 1bab0de0274f ("dm-mpath, scsi_dh: don't let dm detach device handlers")
> Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
> Acked-by: Christoph Hellwig <hch@xxxxxx>
Hello James,
could we get this regression fix before 4.3 is released?
Problem happens like this:
dm-multipath sysadmin
------------------------------------------------------------------
scsi_dh_activate()
[start using handler data]
echo 1 > /sys/block/sdX/device/delete
scsi_remove_device()
scsi_dh_remove_device()
scsi_dh->detach()
kfree(handler data)
[still using freed handler data]
[finish using handler data]
and can result in crash or data corruption.
> ---
> drivers/scsi/scsi_dh.c | 6 +++++-
> drivers/scsi/scsi_priv.h | 2 ++
> drivers/scsi/scsi_sysfs.c | 2 ++
> 3 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_dh.c b/drivers/scsi/scsi_dh.c
> index edb044a..19bf9db 100644
> --- a/drivers/scsi/scsi_dh.c
> +++ b/drivers/scsi/scsi_dh.c
> @@ -232,10 +232,14 @@ int scsi_dh_add_device(struct scsi_device *sdev)
> return err;
> }
>
> -void scsi_dh_remove_device(struct scsi_device *sdev)
> +void scsi_dh_release_device(struct scsi_device *sdev)
> {
> if (sdev->handler)
> scsi_dh_handler_detach(sdev);
> +}
> +
> +void scsi_dh_remove_device(struct scsi_device *sdev)
> +{
> device_remove_file(&sdev->sdev_gendev, &scsi_dh_state_attr);
> }
>
> diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
> index 644bb73..4d01cdb 100644
> --- a/drivers/scsi/scsi_priv.h
> +++ b/drivers/scsi/scsi_priv.h
> @@ -173,9 +173,11 @@ extern struct async_domain scsi_sd_probe_domain;
> /* scsi_dh.c */
> #ifdef CONFIG_SCSI_DH
> int scsi_dh_add_device(struct scsi_device *sdev);
> +void scsi_dh_release_device(struct scsi_device *sdev);
> void scsi_dh_remove_device(struct scsi_device *sdev);
> #else
> static inline int scsi_dh_add_device(struct scsi_device *sdev) { return 0; }
> +static inline void scsi_dh_release_device(struct scsi_device *sdev) { }
> static inline void scsi_dh_remove_device(struct scsi_device *sdev) { }
> #endif
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index b333389..dff8faf 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -399,6 +399,8 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
>
> sdev = container_of(work, struct scsi_device, ew.work);
>
> + scsi_dh_release_device(sdev);
> +
> parent = sdev->sdev_gendev.parent;
>
> spin_lock_irqsave(sdev->host->host_lock, flags);
--
Jun'ichi Nomura, NEC Corporation
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