linux-kernel - Re: [patch -target tree] usb: gadget: f

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Date:	Thu, 10 Mar 2016 09:34:50 +0100
From:	Andrzej Pietrasiewicz <andrzej.p@...sung.com>
To:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
Cc:	Felipe Balbi <balbi@...nel.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Christoph Hellwig <hch@....de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Bart Van Assche <bart.vanassche@...disk.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	target-devel@...r.kernel.org
Subject: Re: [patch -target tree] usb: gadget: f_tcm: use after free

Hi Nicholas,

W dniu 10.03.2016 o 06:19, Nicholas A. Bellinger pisze:
> Hi Andrzej,
>
> On Wed, 2016-03-09 at 13:53 +0100, Andrzej Pietrasiewicz wrote:
>> Hi Nicholas,
>>

<snip>

>
> Applying the following patch to re-add the missing assingment
> as a proper alloc_session callback.
>
> diff --git a/drivers/usb/gadget/function/f_tcm.c b/drivers/usb/gadget/function/f_tcm.c
> index e352a31..348140c 100644
> --- a/drivers/usb/gadget/function/f_tcm.c
> +++ b/drivers/usb/gadget/function/f_tcm.c
> @@ -1570,6 +1570,16 @@ out:
>          return ret;
>   }
>
> +static int usbg_alloc_sess_cb(struct se_portal_group *se_tpg,
> +                             struct se_session *se_sess, void *p)
> +{
> +       struct usbg_tpg *tpg = container_of(se_tpg,
> +                               struct usbg_tpg, se_tpg);
> +
> +       tpg->tpg_nexus = p;
> +       return 0;
> +}
> +
>   static int tcm_usbg_make_nexus(struct usbg_tpg *tpg, char *name)
>   {
>          struct tcm_usbg_nexus *tv_nexus;
> @@ -1591,7 +1601,7 @@ static int tcm_usbg_make_nexus(struct usbg_tpg *tpg, char *name)
>          tv_nexus->tvn_se_sess = target_alloc_session(&tpg->se_tpg, 128,
>                                                       sizeof(struct usbg_cmd),
>                                                       TARGET_PROT_NORMAL, name,
> -                                                    tv_nexus, NULL);
> +                                                    tv_nexus, usbg_alloc_sess_cb);
>          if (IS_ERR(tv_nexus->tvn_se_sess)) {
>   #define MAKE_NEXUS_MSG "core_tpg_check_initiator_node_acl() failed for %s\n"
>                  pr_debug(MAKE_NEXUS_MSG, name);
>

<snip>

>
> Mmmm, usbg_get_cmd() was missing an explicit memset() after tag lookup.
>
> How about the following..?
>
> diff --git a/drivers/usb/gadget/function/f_tcm.c b/drivers/usb/gadget/function/f_tcm.c
> index e352a31..d4e8a91 100644
> --- a/drivers/usb/gadget/function/f_tcm.c
> +++ b/drivers/usb/gadget/function/f_tcm.c
> @@ -1078,6 +1078,7 @@ static struct usbg_cmd *usbg_get_cmd(struct f_uas *fu,
>                  return ERR_PTR(-ENOMEM);
>
>          cmd = &((struct usbg_cmd *)se_sess->sess_cmd_map)[tag];
> +       memset(cmd, 0, sizeof(*cmd));
>          cmd->se_cmd.map_tag = tag;
>          cmd->se_cmd.tag = cmd->tag = scsi_tag;
>          cmd->fu = fu;
>
>
>

I tested it. Works for me.

AP