Messages in this thread Patch in this message | | | From | Samuel Holland <> | Subject | [PATCH 2/3] mailbox: Avoid NULL dereference in mbox_chan_received_data | Date | Tue, 27 Feb 2018 20:27:13 -0600 |
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If a reception IRQ is pending when a mailbox channel is shut down (for example, if the controller uses threaded interrupts), it is possible for mbox_chan_received_data to be called while chan->cl is NULL.
This was found while developing a mailbox controller driver for use with SCPI. The SCPI protocol driver frees its mailbox channel during probing if the SCP firmware does not respond within a specified timeout. In this case, if the SCP firmware takes slightly too long to respond, mbox_chan_received_data races with mbox_free_channel clearing chan->cl.
Signed-off-by: Samuel Holland <samuel@sholland.org> --- drivers/mailbox/mailbox.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c index 674b35f402f5..a0258d8672d5 100644 --- a/drivers/mailbox/mailbox.c +++ b/drivers/mailbox/mailbox.c @@ -152,9 +152,11 @@ static enum hrtimer_restart txdone_hrtimer(struct hrtimer *hrtimer) */ void mbox_chan_received_data(struct mbox_chan *chan, void *mssg) { + struct mbox_client *cl = READ_ONCE(chan->cl); + /* No buffering the received data */ - if (chan->cl->rx_callback) - chan->cl->rx_callback(chan->cl, mssg); + if (cl && cl->rx_callback) + cl->rx_callback(cl, mssg); } EXPORT_SYMBOL_GPL(mbox_chan_received_data); -- 2.13.6
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