Re: [patch -target tree] usb: gadget: f_tcm: use after free

[Andrzej Pietrasiewicz]

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