2016-01-07 11:51:44

by Jia-Ju Bai

Subject: [PATCH] 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->cmd[i], 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.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/net/wireless/iwlegacy/common.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/iwlegacy/common.c b/drivers/net/wireless/iwlegacy/common.c
index 8871145..2656a15 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)
@@ -3076,11 +3080,15 @@ il_tx_queue_init(struct il_priv *il, u32 txq_id)

return 0;
err:
- for (i = 0; i < actual_slots; i++)
+ for (i = 0; i < actual_slots; i++) {
kfree(txq->cmd[i]);
+ txq->cmd[i] = NULL;
+ }
out_free_arrays:
kfree(txq->meta);
+ txq->meta = NULL;
kfree(txq->cmd);
+ txq->cmd = NULL;

return -ENOMEM;
}
--
1.7.9.5

2016-01-11 12:14:04

by Stanislaw Gruszka

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

On Thu, Jan 07, 2016 at 07:51:38PM +0800, Jia-Ju Bai wrote:
> err:
> - for (i = 0; i < actual_slots; i++)
> + for (i = 0; i < actual_slots; i++) {
> kfree(txq->cmd[i]);
> + txq->cmd[i] = NULL;

I don't think we need this, otherwise patch looks good.

Stanislaw