padata: avoid UAF for reorder_work

Although the previous patch can avoid ps and ps UAF for _do_serial, it
can not avoid potential UAF issue for reorder_work. This issue can
happen just as below:

crypto_request			crypto_request		crypto_del_alg
padata_do_serial
  ...
  padata_reorder
    // processes all remaining
    // requests then breaks
    while (1) {
      if (!padata)
        break;
      ...
    }

				padata_do_serial
				  // new request added
				  list_add
    // sees the new request
    queue_work(reorder_work)
				  padata_reorder
				    queue_work_on(squeue->work)
...

				<kworker context>
				padata_serial_worker
				// completes new request,
				// no more outstanding
				// requests

							crypto_del_alg
							  // free pd

<kworker context>
invoke_padata_reorder
  // UAF of pd

To avoid UAF for 'reorder_work', get 'pd' ref before put 'reorder_work'
into the 'serial_wq' and put 'pd' ref until the 'serial_wq' finish.

Fixes: bbefa1dd6a6d ("crypto: pcrypt - Avoid deadlock by using per-instance padata queues")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/kernel/padata.c b/kernel/padata.c
index de2c02a..4189870 100644 (file)
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -352,8 +352,14 @@ static void padata_reorder(struct parallel_data *pd)
        smp_mb();
 
        reorder = per_cpu_ptr(pd->reorder_list, pd->cpu);
-       if (!list_empty(&reorder->list) && padata_find_next(pd, false))
+       if (!list_empty(&reorder->list) && padata_find_next(pd, false)) {
+               /*
+                * Other context(eg. the padata_serial_worker) can finish the request.
+                * To avoid UAF issue, add pd ref here, and put pd ref after reorder_work finish.
+                */
+               padata_get_pd(pd);
                queue_work(pinst->serial_wq, &pd->reorder_work);
+       }
 }
 
 static void invoke_padata_reorder(struct work_struct *work)
@@ -364,6 +370,8 @@ static void invoke_padata_reorder(struct work_struct *work)
        pd = container_of(work, struct parallel_data, reorder_work);
        padata_reorder(pd);
        local_bh_enable();
+       /* Pairs with putting the reorder_work in the serial_wq */
+       padata_put_pd(pd);
 }
 
 static void padata_serial_worker(struct work_struct *serial_work)