mfd: dln2: Add a limit check for invalid echo

The echo field in dln2_transfer_complete comes directly from an USB
transfer and we should not trust it is valid.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/mfd/dln2.c b/drivers/mfd/dln2.c
index cf22841c1e3c..df2fda9cd3db 100644
--- a/drivers/mfd/dln2.c
+++ b/drivers/mfd/dln2.c
@@ -195,6 +195,9 @@ static bool dln2_transfer_complete(struct dln2_dev *dln2, struct urb *urb,
         struct dln2_rx_context *rxc;
         bool valid_slot = false;
 
+        if (rx_slot >= DLN2_MAX_RX_SLOTS)
+                goto out;
+
         rxc = &rxs->slots[rx_slot];
 
         /*
@@ -210,6 +213,7 @@ static bool dln2_transfer_complete(struct dln2_dev *dln2, struct urb *urb,
         }
         spin_unlock(&rxs->lock);
 
+out:
         if (!valid_slot)
                 dev_warn(dev, "bad/late response %d/%d\n", handle, rx_slot);