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UPSTREAM: 9p/xen : Fix use after free bug in xen_9pfs_front_remove due to race condition

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[ Upstream commit ea4f100940 ]

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

Bug: 284409180
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>
(cherry picked from commit 9266e939d7)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I3a50acfe9957e0140e01d17f4d766532ec5670e0
This commit is contained in:
Zheng Wang 2023-03-13 22:43:25 +08:00 • committed by Treehugger Robot
commit 708d51e22a
1 changed files with 4 additions and 0 deletions
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4
net/9p/trans_xen.c
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@ -300,6 +300,10 @@ static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
write_unlock(&xen_9pfs_lock);
for (i = 0; i < priv->num_rings; i++) {
struct xen_9pfs_dataring *ring = &priv->rings[i];
cancel_work_sync(&ring->work);
if (!priv->rings[i].intf)
break;
if (priv->rings[i].irq > 0)