iwlwifi: pcie: fix access to scratch buffer

This fixes a pretty ancient bug that hasn't manifested itself
until now.
The scratchbuf for command queue is allocated only for 32 slots
but is accessed with the queue write pointer - which can be
up to 256.
Since the scratch buf size was 16 and there are up to 256 TFDs
we never passed a page boundary when accessing the scratch buffer,
but when attempting to increase the size of the scratch buffer a
panic was quick to follow when trying to access the address resulted
in a page boundary.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Fixes: 38c0f334b359 ("iwlwifi: use coherent DMA memory for command header")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/tx.c b/drivers/net/wireless/intel/iwlwifi/pcie/tx.c
index 8901d49..9b5858b 100644 (file)
--- a/drivers/net/wireless/intel/iwlwifi/pcie/tx.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/tx.c
@@ -1604,9 +1604,9 @@ static int iwl_pcie_enqueue_hcmd(struct iwl_trans *trans,
 
        /* start the TFD with the scratchbuf */
        scratch_size = min_t(int, copy_size, IWL_HCMD_SCRATCHBUF_SIZE);
-       memcpy(&txq->scratchbufs[q->write_ptr], &out_cmd->hdr, scratch_size);
+       memcpy(&txq->scratchbufs[idx], &out_cmd->hdr, scratch_size);
        iwl_pcie_txq_build_tfd(trans, txq,
-                              iwl_pcie_get_scratchbuf_dma(txq, q->write_ptr),
+                              iwl_pcie_get_scratchbuf_dma(txq, idx),
                               scratch_size, true);
 
        /* map first command fragment, if any remains */