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authorRoger Pau Monne <roger.pau@citrix.com>2021-06-07 15:13:15 +0200
committerJuergen Gross <jgross@suse.com>2021-06-07 15:13:15 +0200
commit107866a8eb0b664675a260f1ba0655010fac1e08 (patch)
tree8c48f10e20935f1d7bf2c725a5f053690db745ba
parentc81d3d24602540f65256f98831d0a25599ea6b87 (diff)
downloadlinux-107866a8eb0b664675a260f1ba0655010fac1e08.tar.bz2
xen-netback: take a reference to the RX task thread
Do this in order to prevent the task from being freed if the thread returns (which can be triggered by the frontend) before the call to kthread_stop done as part of the backend tear down. Not taking the reference will lead to a use-after-free in that scenario. Such reference was taken before but dropped as part of the rework done in 2ac061ce97f4. Reintroduce the reference taking and add a comment this time explaining why it's needed. This is XSA-374 / CVE-2021-28691. Fixes: 2ac061ce97f4 ('xen/netback: cleanup init and deinit code') Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Cc: stable@vger.kernel.org Reviewed-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com>
-rw-r--r--drivers/net/xen-netback/interface.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 193b723fe3bd..c58996c1e230 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -684,6 +684,7 @@ static void xenvif_disconnect_queue(struct xenvif_queue *queue)
{
if (queue->task) {
kthread_stop(queue->task);
+ put_task_struct(queue->task);
queue->task = NULL;
}
@@ -745,6 +746,11 @@ int xenvif_connect_data(struct xenvif_queue *queue,
if (IS_ERR(task))
goto kthread_err;
queue->task = task;
+ /*
+ * Take a reference to the task in order to prevent it from being freed
+ * if the thread function returns before kthread_stop is called.
+ */
+ get_task_struct(task);
task = kthread_run(xenvif_dealloc_kthread, queue,
"%s-dealloc", queue->name);