[PATCH] wifi: wfx: fix memory corruption by limiting max_rates to 4

[Lech Perczak <lech.perczak@camlingroup.com>]

From: Paweł Lenkow <pawel.lenkow@camlingroup.com>

During our testing of WFM200 module over SDIO on i.MX6Q-based platform,
we discovered a memory corruption on the system, tracing back to the wfx
driver. Using kfence, it was possible to trace it back to the root
cause, which is hw->max_rates set to 8 in wfx_init_common,
while the maximum defined by IEEE80211_TX_TABLE_SIZE is 4.

This causes array out-of-bounds writes during updates of the rate table,
as seen below:

BUG: KFENCE: memory corruption in kfree_rcu_work+0x320/0x36c

Corrupted memory at 0xe0a4ffe0 [ 0x03 0x03 0x03 0x03 0x01 0x00 0x00
 0x02 0x02 0x02 0x09 0x00 0x21 0xbb 0xbb 0xbb ] (in kfence-#81):
 kfree_rcu_work+0x320/0x36c
 process_one_work+0x3ec/0x920
 worker_thread+0x60/0x7a4
 kthread+0x174/0x1b4
 ret_from_fork+0x14/0x2c
 0x0

kfence-#81: 0xe0a4ffc0-0xe0a4ffdf, size=32, cache=kmalloc-64

allocated by task 297 on cpu 0 at 631.039555s:
 minstrel_ht_update_rates+0x38/0x2b0 [mac80211]
 rate_control_tx_status+0xb4/0x148 [mac80211]
 ieee80211_tx_status_ext+0x364/0x1030 [mac80211]
 ieee80211_tx_status+0xe0/0x118 [mac80211]
 ieee80211_tasklet_handler+0xb0/0xe0 [mac80211]
 tasklet_action_common.constprop.0+0x11c/0x148
 __do_softirq+0x1a4/0x61c
 irq_exit+0xcc/0x104
 call_with_stack+0x18/0x20
 __irq_svc+0x80/0xb0
 wq_worker_sleeping+0x10/0x100
 wq_worker_sleeping+0x10/0x100
 schedule+0x50/0xe0
 schedule_timeout+0x2e0/0x474
 wait_for_completion+0xdc/0x1ec
 mmc_wait_for_req_done+0xc4/0xf8
 mmc_io_rw_extended+0x3b4/0x4ec
 sdio_io_rw_ext_helper+0x290/0x384
 sdio_memcpy_toio+0x30/0x38
 wfx_sdio_copy_to_io+0x88/0x108 [wfx]
 wfx_data_write+0x88/0x1f0 [wfx]
 bh_work+0x1c8/0xcc0 [wfx]
 process_one_work+0x3ec/0x920
 worker_thread+0x60/0x7a4
 kthread+0x174/0x1b4
 ret_from_fork+0x14/0x2c 0x0

Limit hw->max_rates to not exceed IEEE80211_TX_RATE_TABLE_SIZE (4).

To bring back previous value, the global table size limit needs to be
increased beforehand in mac80211.h, or by limiting the iteration count
in minstrel_ht_update_rates against IEEE80211_TX_RATE_TABLE_SIZE as
well.

Fixes: e16e7f0716a6 ("staging: wfx: instantiate mac80211 data")
Cc: Jérôme Pouiller <jerome.pouiller@silabs.com>
Cc: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/all/12e5adcd-8aed-f0f7-70cc-4fb7b656b829@camlingroup.com/

Signed-off-by: Paweł Lenkow <pawel.lenkow@camlingroup.com>
Signed-off-by: Lech Perczak <lech.perczak@camlingroup.com>
---
 drivers/net/wireless/silabs/wfx/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/silabs/wfx/main.c b/drivers/net/wireless/silabs/wfx/main.c
index 84d82ddded56..7463fe4b5cae 100644
--- a/drivers/net/wireless/silabs/wfx/main.c
+++ b/drivers/net/wireless/silabs/wfx/main.c
@@ -273,7 +273,7 @@ struct wfx_dev *wfx_init_common(struct device *dev, const struct wfx_platform_da
 	hw->vif_data_size = sizeof(struct wfx_vif);
 	hw->sta_data_size = sizeof(struct wfx_sta_priv);
 	hw->queues = 4;
-	hw->max_rates = 8;
+	hw->max_rates = 4;
 	hw->max_rate_tries = 8;
 	hw->extra_tx_headroom = sizeof(struct wfx_hif_msg) + sizeof(struct wfx_hif_req_tx) +
 				4 /* alignment */ + 8 /* TKIP IV */;
-- 
2.25.1