Re: [PATCH v1] driver core: Use list_del_init to replace list_del at device_links_purge()

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

On 08/01/2020 11:34, Luo Jiaxing wrote:

+ linux-scsi, Martin

> We found that enabling kernel compilation options CONFIG_SCSI_ENCLOSURE and
> CONFIG_ENCLOSURE_SERVICES, repeated initialization and deletion of the same
> SCSI device will cause system panic, as follows:
> [72.425705] Unable to handle kernel paging request at virtual address
> dead000000000108
> ...
> [72.595093] Call trace:
> [72.597532] device_del + 0x194 / 0x3a0
> [72.601012] enclosure_remove_device + 0xbc / 0xf8
> [72.605445] ses_intf_remove + 0x9c / 0xd8
> [72.609185] device_del + 0xf8 / 0x3a0
> [72.612576] device_unregister + 0x14 / 0x30
> [72.616489] __scsi_remove_device + 0xf4 / 0x140
> [72.620747] scsi_remove_device + 0x28 / 0x40
> [72.624745] scsi_remove_target + 0x1c8 / 0x220

please share the full crash stack frame and the commands used to trigger 
it. Some people prefer the timestamp removed also.

> 
> After analysis, we see that in the error scenario, the ses module has the
> following calling sequence:
> device_register() -> device_del() -> device_add() -> device_del().
> The first call to device_del() is fine, but the second call to device_del()
> will cause a system panic.
> 
> Through disassembly, we locate that panic happen when device_links_purge()
> call list_del() to remove device_links.needs_suppliers from list, and
> list_del() will set this list entry's prev and next pointers to poison.
> So if INIT_LIST_HEAD() is not re-executed before the next list_del(), It
> will cause the system to access a memory address which is posioned.
> 
> Therefore, replace list_del() with list_del_init() can avoid such issue.
> 
> Fixes: e2ae9bcc4aaa ("driver core: Add support for linking devices during device addition")
> Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
> Reviewed-by: John Garry <john.garry@huawei.com>

This tag was only implicitly granted, but I thought that the fix looked 
ok, so:

Reviewed-by: John Garry <john.garry@huawei.com>

> ---
>   drivers/base/core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 42a6724..7b9b0d6 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -1103,7 +1103,7 @@ static void device_links_purge(struct device *dev)
>   	struct device_link *link, *ln;
>   
>   	mutex_lock(&wfs_lock);
> -	list_del(&dev->links.needs_suppliers);
> +	list_del_init(&dev->links.needs_suppliers);
>   	mutex_unlock(&wfs_lock);
>   
>   	/*
>