Patch "padata: avoid UAF for reorder_work" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    padata: avoid UAF for reorder_work

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     padata-avoid-uaf-for-reorder_work.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 2aee1b9354dccccd72d4b1e2172393719af48433
Author: Chen Ridong <chenridong@xxxxxxxxxx>
Date:   Fri Jan 10 06:16:39 2025 +0000

    padata: avoid UAF for reorder_work
    
    [ Upstream commit dd7d37ccf6b11f3d95e797ebe4e9e886d0332600 ]
    
    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@xxxxxxxxxx>
    Acked-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
    Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/padata.c b/kernel/padata.c
index 02bb06a2c797d..c7aa60907fdf8 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -357,8 +357,14 @@ 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)
@@ -369,6 +375,8 @@ 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)