Re: [PATCH V2 1/2] scsi: core: fix failure handling of scsi_add_host_with_dma

[John Garry <john.garry@huawei.com>]

On 28/05/2021 02:18, Ming Lei wrote:
> When scsi_add_host_with_dma() return failure, the caller will call
> scsi_host_put(shost) to release everything allocated for this host
> instance. So we can't free allocated stuff in scsi_add_host_with_dma(),
> otherwise double free will be caused.
> 
> Strictly speaking, these host resources allocation should have been
> moved to scsi_host_alloc(), but the allocation may need driver's
> info which can be built between calling scsi_host_alloc() and
> scsi_add_host(), so just keep the allocations in
> scsi_add_host_with_dma().
> 
> Fixes the problem by relying on host device's release handler to
> release everything.
> 
> Cc: Bart Van Assche <bvanassche@acm.org>
> Cc: John Garry <john.garry@huawei.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>

It now looks like we have a memory leak:

unreferenced object 0xffff0410070a4e00 (size 128):
   comm "swapper/0", pid 1, jiffies 4294894100 (age 90.744s)
   hex dump (first 32 bytes):
68 6f 73 74 30 00 00 00 00 00 00 00 00 00 00 00  host0...........
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
   backtrace:
[<(____ptrval____)>] __kmalloc_track_caller+0x25c/0x380
[<(____ptrval____)>] kvasprintf+0xe8/0x1a4
[<(____ptrval____)>] kvasprintf_const+0xc8/0x17c
[<(____ptrval____)>] kobject_set_name_vargs+0x58/0xf4
[<(____ptrval____)>] dev_set_name+0xa4/0xe0
[<(____ptrval____)>] scsi_host_alloc+0x45c/0x5d0
[<(____ptrval____)>] hisi_sas_probe+0x40/0x570
[<(____ptrval____)>] hisi_sas_v2_probe+0x1c/0x2c
[<(____ptrval____)>] platform_probe+0x90/0x110
[<(____ptrval____)>] really_probe+0x148/0x744
[<(____ptrval____)>] driver_probe_device+0x8c/0xfc
[<(____ptrval____)>] device_driver_attach+0x11c/0x12c
[<(____ptrval____)>] __driver_attach+0xc8/0x1a0
[<(____ptrval____)>] bus_for_each_dev+0xe4/0x154
[<(____ptrval____)>] driver_attach+0x38/0x50
[<(____ptrval____)>] bus_add_driver+0x1bc/0x2c4
unreferenced object 0xffff001056581800 (size 256):
   comm "swapper/0", pid 1, jiffies 4294894398 (age 89.560s)
   hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 08 18 58 56 10 00 ff ff  ..........XV....
08 18 58 56 10 00 ff ff c0 f4 b4 10 00 80 ff ff  ..XV............
   backtrace:
[<(____ptrval____)>] kmem_cache_alloc+0x298/0x350
[<(____ptrval____)>] device_add+0x6d8/0xc4c
[<(____ptrval____)>] scsi_add_host_with_dma+0x370/0x5dc
[<(____ptrval____)>] hisi_sas_probe+0x418/0x570
[<(____ptrval____)>] hisi_sas_v2_probe+0x1c/0x2c
[<(____ptrval____)>] platform_probe+0x90/0x110
[<(____ptrval____)>] really_probe+0x148/0x744
[<(____ptrval____)>] driver_probe_device+0x8c/0xfc
[<(____ptrval____)>] device_driver_attach+0x11c/0x12c
[<(____ptrval[  101.941505] random: fast init done
____)>] __driver_attach+0xc8/0x1a0
[<(____ptrval____)>] bus_for_each_dev+0xe4/0x154
[<(____ptrval____)>] driver_attach+0x38/0x50
[<(____ptrval____)>] bus_add_driver+0x1bc/0x2c4
[<(____ptrval____)>] driver_register+0xe4/0x210
[<(____ptrval____)>] __platform_driver_register+0x48/0x60
[<(____ptrval____)>] hisi_sas_v2_driver_init+0x20/0x2c

I think that the release for the shost_dev dev name memory needs fixing.

In scsi_host_dev_release(), for my experiment, shost state is running, 
so we miss the kfree(dev_name(&shost->shost_dev)), I guess. Not sure on 
the proper fix.

> ---
>   drivers/scsi/hosts.c | 14 ++++++--------
>   1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index 697c09ef259b..ea50856cb203 100644
> --- a/drivers/scsi/hosts.c
> +++ b/drivers/scsi/hosts.c
> @@ -278,23 +278,22 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
>   
>   		if (!shost->work_q) {
>   			error = -EINVAL;
> -			goto out_free_shost_data;
> +			goto out_del_dev;
>   		}
>   	}
>   
>   	error = scsi_sysfs_add_host(shost);
>   	if (error)
> -		goto out_destroy_host;
> +		goto out_del_dev;
>   
>   	scsi_proc_host_add(shost);
>   	scsi_autopm_put_host(shost);
>   	return error;
>   
> - out_destroy_host:
> -	if (shost->work_q)
> -		destroy_workqueue(shost->work_q);
> - out_free_shost_data:
> -	kfree(shost->shost_data);
> +	/*
> +	 * any host allocation in this function will be freed in
> +	 * scsi_host_dev_release, so not free them in the failure path

nit: "so do not free them"

> +	 */
>    out_del_dev:
>   	device_del(&shost->shost_dev);
>    out_del_gendev:
> @@ -304,7 +303,6 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
>   	pm_runtime_disable(&shost->shost_gendev);
>   	pm_runtime_set_suspended(&shost->shost_gendev);
>   	pm_runtime_put_noidle(&shost->shost_gendev);
> -	scsi_mq_destroy_tags(shost);
>    fail:
>   	return error;
>   }
> 

Thanks,
John