Author: royger
Date: Thu May 24 10:18:31 2018
New Revision: 334144
URL: https://svnweb.freebsd.org/changeset/base/334144
Log:
dev/xenstore: prevent transaction hijacking
The user-space xenstore device is currently lacking a check to make
sure that the caller is only using transaction ids currently assigned
to it. This allows users of the xenstore device to hijack transactions
not started by them, although the scope is limited to transactions
started by the same domain.
Tested by: Nathan Friess <nathan.fri...@gmail.com>
Sponsored by: Citrix Systems R&D
Modified:
head/sys/dev/xen/xenstore/xenstore_dev.c
Modified: head/sys/dev/xen/xenstore/xenstore_dev.c
==============================================================================
--- head/sys/dev/xen/xenstore/xenstore_dev.c Thu May 24 10:18:14 2018
(r334143)
+++ head/sys/dev/xen/xenstore/xenstore_dev.c Thu May 24 10:18:31 2018
(r334144)
@@ -214,6 +214,18 @@ xs_dev_watch_cb(struct xs_watch *watch, const char **v
free(payload, M_XENSTORE);
}
+static struct xs_dev_transaction *
+xs_dev_find_transaction(struct xs_dev_data *u, uint32_t tx_id)
+{
+ struct xs_dev_transaction *trans;
+
+ LIST_FOREACH(trans, &u->transactions, list)
+ if (trans->handle.id == tx_id)
+ return (trans);
+
+ return (NULL);
+}
+
static int
xs_dev_read(struct cdev *dev, struct uio *uio, int ioflag)
{
@@ -281,6 +293,12 @@ xs_dev_write(struct cdev *dev, struct uio *uio, int io
case XS_MKDIR:
case XS_RM:
case XS_SET_PERMS:
+ /* Check that this transaction id is not hijacked. */
+ if (u->u.msg.tx_id != 0 &&
+ xs_dev_find_transaction(u, u->u.msg.tx_id) == NULL) {
+ error = EINVAL;
+ break;
+ }
error = xs_dev_request_and_reply(&u->u.msg, &reply);
if (!error) {
if (u->u.msg.type == XS_TRANSACTION_START) {
@@ -289,12 +307,10 @@ xs_dev_write(struct cdev *dev, struct uio *uio, int io
trans->handle.id = strtoul(reply, NULL, 0);
LIST_INSERT_HEAD(&u->transactions, trans, list);
} else if (u->u.msg.type == XS_TRANSACTION_END) {
- LIST_FOREACH(trans, &u->transactions, list)
- if (trans->handle.id == u->u.msg.tx_id)
- break;
-#if 0 /* XXX does this mean the list is empty? */
- BUG_ON(&trans->list == &u->transactions);
-#endif
+ trans = xs_dev_find_transaction(u,
+ u->u.msg.tx_id);
+ KASSERT(trans != NULL,
+ ("Unable to find transaction"));
LIST_REMOVE(trans, list);
free(trans, M_XENSTORE);
}
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