Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.10 136/137] xen-netback: take a reference to the RX task thread | Date | Tue, 8 Jun 2021 20:27:56 +0200 |
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From: Roger Pau Monne <roger.pau@citrix.com>
commit 107866a8eb0b664675a260f1ba0655010fac1e08 upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/net/xen-netback/interface.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -685,6 +685,7 @@ static void xenvif_disconnect_queue(stru { 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_qu 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);
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