From: Sara Sharon <>

3.12-stable review patch.  If anyone has any objections, please let me know.


commit d5d0689aefc59c6a5352ca25d7e6d47d03f543ce upstream.

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 <>
Fixes: 38c0f334b359 ("iwlwifi: use coherent DMA memory for command header")
Signed-off-by: Luca Coelho <>
Signed-off-by: Jiri Slaby <>
 drivers/net/wireless/iwlwifi/pcie/tx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/iwlwifi/pcie/tx.c 
index 911a15074ffb..6c769009587b 100644
--- a/drivers/net/wireless/iwlwifi/pcie/tx.c
+++ b/drivers/net/wireless/iwlwifi/pcie/tx.c
@@ -1328,9 +1328,9 @@ 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, 1);
        /* map first command fragment, if any remains */

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