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9p/xen : Fix use after free bug in xen_9pfs_front_remove due to race condition
[ Upstream commitea4f100940
] 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:71ebd71921
("xen/9pfs: connect to the backend") Signed-off-by: Zheng Wang <zyytlz.wz@163.com> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com> Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -280,6 +280,10 @@ static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
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write_unlock(&xen_9pfs_lock);
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for (i = 0; i < priv->num_rings; i++) {
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struct xen_9pfs_dataring *ring = &priv->rings[i];
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cancel_work_sync(&ring->work);
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if (!priv->rings[i].intf)
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break;
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if (priv->rings[i].irq > 0)
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