[PATCH v2] iwl4965: Fix a null pointer dereference in il_tx_queue_free and il_cmd_queue_free

[PATCH v2] iwl4965: Fix a null pointer dereference in il_tx_queue_free and il_cmd_queue_free

[Jia-Ju Bai]

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>
---
 drivers/net/wireless/iwlegacy/common.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/iwlegacy/common.c b/drivers/net/wireless/iwlegacy/common.c
index 8871145..092ecbc 100644
--- a/drivers/net/wireless/iwlegacy/common.c
+++ b/drivers/net/wireless/iwlegacy/common.c
@@ -2794,8 +2794,10 @@ 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)
@@ -2873,8 +2875,10 @@ 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)
@@ -3080,7 +3084,9 @@ err:
 		kfree(txq->cmd[i]);
 out_free_arrays:
 	kfree(txq->meta);
+	txq->meta = NULL;
 	kfree(txq->cmd);
+	txq->cmd = NULL;
 
 	return -ENOMEM;
 }
-- 
1.7.9.5

Re: [PATCH v2] iwl4965: Fix a null pointer dereference in il_tx_queue_free and il_cmd_queue_free

[Stanislaw Gruszka]

On Mon, Jan 11, 2016 at 09:42:54PM +0800, Jia-Ju Bai wrote:
> 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 <baijiaju1990-9Onoh4P/yGk@public.gmane.org>

Acked-by: Stanislaw Gruszka <sgruszka-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html