iwl4965: Fix a null pointer dereference in il_tx_queue_free and il_cmd_queue_free

If "txq->cmd = kzalloc(...)" in il_tx_queue_init fails,
"kfree(txq->cmd[i])" in il_tx_queue_free and il_cmd_queue_free
in iwl4965_hw_txq_ctx_free will causes a null pointer dereference,
because txq->cmd is NULL at that time.

This patch fixes this problem by adding a if-check before kfree.
To avoid double free in il_tx_queue_free and il_cmd_queue_free
caused by the fixing, txq->meta and txq->cmd in error handling code
of il_tx_queue_init are assigned null values.
Otherwise, a double free will occur.

This patch has been tested in real device, and it actually fixes the bug.
Thanks Stanislaw for his suggestion.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Acked-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

diff --git a/drivers/net/wireless/intel/iwlegacy/common.c b/drivers/net/wireless/intel/iwlegacy/common.c
index c3afaf71066eb1e6560c79ba62cf1b8df5970281..2cc3d42bbab7cc5af5f1cd16e64740052c7b92bd 100644 (file)
--- a/drivers/net/wireless/intel/iwlegacy/common.c
+++ b/drivers/net/wireless/intel/iwlegacy/common.c
@@ -2792,8 +2792,10 @@ il_tx_queue_free(struct il_priv *il, int txq_id)
        il_tx_queue_unmap(il, txq_id);
 
        /* De-alloc array of command/tx buffers */
-       for (i = 0; i < TFD_TX_CMD_SLOTS; i++)
-               kfree(txq->cmd[i]);
+       if (txq->cmd) {
+               for (i = 0; i < TFD_TX_CMD_SLOTS; i++)
+                       kfree(txq->cmd[i]);
+       }
 
        /* De-alloc circular buffer of TFDs */
        if (txq->q.n_bd)
@@ -2871,8 +2873,10 @@ il_cmd_queue_free(struct il_priv *il)
        il_cmd_queue_unmap(il);
 
        /* De-alloc array of command/tx buffers */
-       for (i = 0; i <= TFD_CMD_SLOTS; i++)
-               kfree(txq->cmd[i]);
+       if (txq->cmd) {
+               for (i = 0; i <= TFD_CMD_SLOTS; i++)
+                       kfree(txq->cmd[i]);
+       }
 
        /* De-alloc circular buffer of TFDs */
        if (txq->q.n_bd)
@@ -3078,7 +3082,9 @@ err:
                kfree(txq->cmd[i]);
 out_free_arrays:
        kfree(txq->meta);
+       txq->meta = NULL;
        kfree(txq->cmd);
+       txq->cmd = NULL;
 
        return -ENOMEM;
 }