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Date: Mon, 13 Mar 2023 12:13:03 +0800 From: Zheng Wang <zyytlz.wz@....com> To: ericvh@...il.com Cc: lucho@...kov.net, asmadeus@...ewreck.org, linux_oss@...debyte.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, v9fs-developer@...ts.sourceforge.net, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, hackerzheng666@...il.com, 1395428693sheep@...il.com, alex000young@...il.com, Zheng Wang <zyytlz.wz@....com> Subject: [PATCH net] 9p/xen : Fix use after free bug in xen_9pfs_front_remove due to race condition In xen_9pfs_front_probe, it calls xen_9pfs_front_alloc_dataring to init priv->rings and bound &ring->work with p9_xen_response. When it calls xen_9pfs_front_event_handler to handle IRQ requests, it will finally call schedule_work to start the work. When we call xen_9pfs_front_remove to remove the driver, there may be a sequence as follows: Fix it by finishing the work before cleanup in xen_9pfs_front_free. Note that, this bug is found by static analysis, which might be false positive. CPU0 CPU1 |p9_xen_response xen_9pfs_front_remove| xen_9pfs_front_free| kfree(priv) | //free priv | |p9_tag_lookup |//use priv->client Fixes: 71ebd71921e4 ("xen/9pfs: connect to the backend") Signed-off-by: Zheng Wang <zyytlz.wz@....com> --- net/9p/trans_xen.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c index c64050e839ac..60adb3aadd63 100644 --- a/net/9p/trans_xen.c +++ b/net/9p/trans_xen.c @@ -274,16 +274,21 @@ static const struct xenbus_device_id xen_9pfs_front_ids[] = { static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv) { int i, j; + struct xen_9pfs_dataring *ring = NULL; write_lock(&xen_9pfs_lock); list_del(&priv->list); write_unlock(&xen_9pfs_lock); for (i = 0; i < priv->num_rings; i++) { + ring = priv->rings[i]; if (!priv->rings[i].intf) break; if (priv->rings[i].irq > 0) unbind_from_irqhandler(priv->rings[i].irq, priv->dev); + + cancel_work_sync(&ring->work); + if (priv->rings[i].data.in) { for (j = 0; j < (1 << priv->rings[i].intf->ring_order); -- 2.25.1
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