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

["Jérôme Pouiller" <jerome.pouiller@silabs.com>]

[Add Peter in Cc:]

On Thursday 15 September 2022 15:14:45 CEST Lech Perczak wrote:
> 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")

I think the issue has been introduced by ee0e16ab756a ("mac80211:
minstrel_ht: fill all requested rates").


> Cc: Jérôme Pouiller <jerome.pouiller@silabs.com>
> Cc: Kalle Valo <kvalo@kernel.org>
> Link: https://urldefense.com/v3/__https://lore.kernel.org/all/12e5adcd-8aed-f0f7-70cc-4fb7b656b829@camlingroup.com/__;!!N30Cs7Jr!ReVaYMRjWoJzG95KRgrZTGAw0bmt5lnLLpRkt574SRvIoKLD2xl53YKUiLpN4PfXpjSLIQ9KvgVy9Wi4jeJE8axP9M4Odgk$
> 
> 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 */;

Do you think the fix should rather be:

------8<----------8<--------
--- i/net/mac80211/rc80211_minstrel_ht.c
+++ w/net/mac80211/rc80211_minstrel_ht.c
@@ -1559,7 +1559,7 @@ minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
        minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate[0]);

        /* Fill up remaining, keep one entry for max_probe_rate */
-       for (; i < (mp->hw->max_rates - 1); i++)
+       for (; i < min(mp->hw->max_rates, IEEE80211_TX_RATE_TABLE_SIZE) - 1; i++)
                minstrel_ht_set_rate(mp, mi, rates, i, mi->max_tp_rate[i]);

        if (i < mp->hw->max_rates)
------8<----------8<--------



-- 
Jérôme Pouiller