Patch "usb: mtu3: fix kernel panic at qmu transfer done irq handler" has been added to the 6.3-stable tree

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

    usb: mtu3: fix kernel panic at qmu transfer done irq handler

to the 6.3-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:
     usb-mtu3-fix-kernel-panic-at-qmu-transfer-done-irq-h.patch
and it can be found in the queue-6.3 subdirectory.

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



commit af26cb45acd036d6c90b38d99e2a7411039fc153
Author: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
Date:   Mon Apr 17 10:51:59 2023 +0800

    usb: mtu3: fix kernel panic at qmu transfer done irq handler
    
    [ Upstream commit d28f4091ea7ec3510fd6a3c6d433234e7a2bef14 ]
    
    When handle qmu transfer irq, it will unlock @mtu->lock before give back
    request, if another thread handle disconnect event at the same time, and
    try to disable ep, it may lock @mtu->lock and free qmu ring, then qmu
    irq hanlder may get a NULL gpd, avoid the KE by checking gpd's value before
    handling it.
    
    e.g.
    qmu done irq on cpu0                 thread running on cpu1
    
    qmu_done_tx()
      handle gpd [0]
        mtu3_requ_complete()        mtu3_gadget_ep_disable()
          unlock @mtu->lock
            give back request         lock @mtu->lock
                                        mtu3_ep_disable()
                                          mtu3_gpd_ring_free()
                                       unlock @mtu->lock
          lock @mtu->lock
        get next gpd [1]
    
    [1]: goto [0] to handle next gpd, and next gpd may be NULL.
    
    Fixes: 48e0d3735aa5 ("usb: mtu3: supports new QMU format")
    Signed-off-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230417025203.18097-3-chunfeng.yun@xxxxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/usb/mtu3/mtu3_qmu.c b/drivers/usb/mtu3/mtu3_qmu.c
index a2fdab8b63b28..3b68a0a19cc76 100644
--- a/drivers/usb/mtu3/mtu3_qmu.c
+++ b/drivers/usb/mtu3/mtu3_qmu.c
@@ -210,6 +210,7 @@ static struct qmu_gpd *advance_enq_gpd(struct mtu3_gpd_ring *ring)
 	return ring->enqueue;
 }
 
+/* @dequeue may be NULL if ring is unallocated or freed */
 static struct qmu_gpd *advance_deq_gpd(struct mtu3_gpd_ring *ring)
 {
 	if (ring->dequeue < ring->end)
@@ -491,7 +492,7 @@ static void qmu_done_tx(struct mtu3 *mtu, u8 epnum)
 	dev_dbg(mtu->dev, "%s EP%d, last=%p, current=%p, enq=%p\n",
 		__func__, epnum, gpd, gpd_current, ring->enqueue);
 
-	while (gpd != gpd_current && !GET_GPD_HWO(gpd)) {
+	while (gpd && gpd != gpd_current && !GET_GPD_HWO(gpd)) {
 
 		mreq = next_request(mep);
 
@@ -530,7 +531,7 @@ static void qmu_done_rx(struct mtu3 *mtu, u8 epnum)
 	dev_dbg(mtu->dev, "%s EP%d, last=%p, current=%p, enq=%p\n",
 		__func__, epnum, gpd, gpd_current, ring->enqueue);
 
-	while (gpd != gpd_current && !GET_GPD_HWO(gpd)) {
+	while (gpd && gpd != gpd_current && !GET_GPD_HWO(gpd)) {
 
 		mreq = next_request(mep);
 



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