2013-04-12 00:53:27

by Bing Zhao

[permalink] [raw]
Subject: [PATCH 1/2] mwifiex: fix use-after-free in beacon_ie processing

beacon_ie buffer is allocated in mwifiex_fill_new_bss_desc()
and the buffer pointer is saved in bss_desc->beacon_buf.
beacon_ie is freed before the function returns. However,
bss_desc->beacon_buf is still being accessed afterwards.

Fix it by freeing beacon_ie (bss_desc->beacon_buf) in
caller's scope.

Reviewed-by: Doug Anderson <[email protected]>
Reviewed-by: Paul Stewart <[email protected]>
Signed-off-by: Bing Zhao <[email protected]>
---
drivers/net/wireless/mwifiex/scan.c | 8 ++++++++
drivers/net/wireless/mwifiex/sta_ioctl.c | 14 +++++++++-----
2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/mwifiex/scan.c b/drivers/net/wireless/mwifiex/scan.c
index e7f6dea..37b24e8 100644
--- a/drivers/net/wireless/mwifiex/scan.c
+++ b/drivers/net/wireless/mwifiex/scan.c
@@ -1533,10 +1533,18 @@ static int mwifiex_update_curr_bss_params(struct mwifiex_private *priv,
/* Make a copy of current BSSID descriptor */
memcpy(&priv->curr_bss_params.bss_descriptor, bss_desc,
sizeof(priv->curr_bss_params.bss_descriptor));
+
+ /* The contents of beacon_ie will be copied to its own buffer
+ * in mwifiex_save_curr_bcn()
+ */
mwifiex_save_curr_bcn(priv);
spin_unlock_irqrestore(&priv->curr_bcn_buf_lock, flags);

done:
+ /* beacon_ie buffer was allocated in function
+ * mwifiex_fill_new_bss_desc(). Free it now.
+ */
+ kfree(bss_desc->beacon_buf);
kfree(bss_desc);
return 0;
}
diff --git a/drivers/net/wireless/mwifiex/sta_ioctl.c b/drivers/net/wireless/mwifiex/sta_ioctl.c
index e6c9b2a..27729cf 100644
--- a/drivers/net/wireless/mwifiex/sta_ioctl.c
+++ b/drivers/net/wireless/mwifiex/sta_ioctl.c
@@ -140,12 +140,13 @@ int mwifiex_request_set_multicast_list(struct mwifiex_private *priv,
/*
* This function fills bss descriptor structure using provided
* information.
+ * beacon_ie buffer is allocated in this function. It is caller's
+ * responsibility to free the memory.
*/
int mwifiex_fill_new_bss_desc(struct mwifiex_private *priv,
struct cfg80211_bss *bss,
struct mwifiex_bssdescriptor *bss_desc)
{
- int ret;
u8 *beacon_ie;
size_t beacon_ie_len;
struct mwifiex_bss_priv *bss_priv = (void *)bss->priv;
@@ -165,6 +166,7 @@ int mwifiex_fill_new_bss_desc(struct mwifiex_private *priv,

memcpy(bss_desc->mac_address, bss->bssid, ETH_ALEN);
bss_desc->rssi = bss->signal;
+ /* The caller of this function will free beacon_ie */
bss_desc->beacon_buf = beacon_ie;
bss_desc->beacon_buf_size = beacon_ie_len;
bss_desc->beacon_period = bss->beacon_interval;
@@ -182,10 +184,7 @@ int mwifiex_fill_new_bss_desc(struct mwifiex_private *priv,
else
bss_desc->bss_mode = NL80211_IFTYPE_STATION;

- ret = mwifiex_update_bss_desc_with_ie(priv->adapter, bss_desc);
-
- kfree(beacon_ie);
- return ret;
+ return mwifiex_update_bss_desc_with_ie(priv->adapter, bss_desc);
}

static int mwifiex_process_country_ie(struct mwifiex_private *priv,
@@ -349,6 +348,11 @@ int mwifiex_bss_start(struct mwifiex_private *priv, struct cfg80211_bss *bss,
}

done:
+ /* beacon_ie buffer was allocated in function
+ * mwifiex_fill_new_bss_desc(). Free it now.
+ */
+ if (bss_desc)
+ kfree(bss_desc->beacon_buf);
kfree(bss_desc);
return ret;
}
--
1.7.0.2



2013-04-12 00:53:27

by Bing Zhao

[permalink] [raw]
Subject: [PATCH 2/2] mwifiex: remove redundant initialization for bss_descriptor

Initialization of bss_descriptor is unnecessary as the entire
structure will be overwritten by a memcpy.

Reported-by: Doug Anderson <[email protected]>
Reviewed-by: Doug Anderson <[email protected]>
Reviewed-by: Paul Stewart <[email protected]>
Signed-off-by: Bing Zhao <[email protected]>
Signed-off-by: Yogesh Ashok Powar <[email protected]>
---
drivers/net/wireless/mwifiex/scan.c | 29 -----------------------------
1 files changed, 0 insertions(+), 29 deletions(-)

diff --git a/drivers/net/wireless/mwifiex/scan.c b/drivers/net/wireless/mwifiex/scan.c
index 37b24e8..9cf5d8f 100644
--- a/drivers/net/wireless/mwifiex/scan.c
+++ b/drivers/net/wireless/mwifiex/scan.c
@@ -1500,36 +1500,7 @@ static int mwifiex_update_curr_bss_params(struct mwifiex_private *priv,
if (ret)
goto done;

- /* Update current bss descriptor parameters */
spin_lock_irqsave(&priv->curr_bcn_buf_lock, flags);
- priv->curr_bss_params.bss_descriptor.bcn_wpa_ie = NULL;
- priv->curr_bss_params.bss_descriptor.wpa_offset = 0;
- priv->curr_bss_params.bss_descriptor.bcn_rsn_ie = NULL;
- priv->curr_bss_params.bss_descriptor.rsn_offset = 0;
- priv->curr_bss_params.bss_descriptor.bcn_wapi_ie = NULL;
- priv->curr_bss_params.bss_descriptor.wapi_offset = 0;
- priv->curr_bss_params.bss_descriptor.bcn_ht_cap = NULL;
- priv->curr_bss_params.bss_descriptor.ht_cap_offset = 0;
- priv->curr_bss_params.bss_descriptor.bcn_ht_oper = NULL;
- priv->curr_bss_params.bss_descriptor.ht_info_offset = 0;
- priv->curr_bss_params.bss_descriptor.bcn_bss_co_2040 = NULL;
- priv->curr_bss_params.bss_descriptor.bss_co_2040_offset = 0;
- priv->curr_bss_params.bss_descriptor.bcn_ext_cap = NULL;
- priv->curr_bss_params.bss_descriptor.ext_cap_offset = 0;
- priv->curr_bss_params.bss_descriptor.beacon_buf = NULL;
- priv->curr_bss_params.bss_descriptor.beacon_buf_size = 0;
- priv->curr_bss_params.bss_descriptor.bcn_vht_cap = NULL;
- priv->curr_bss_params.bss_descriptor.vht_cap_offset = 0;
- priv->curr_bss_params.bss_descriptor.bcn_vht_oper = NULL;
- priv->curr_bss_params.bss_descriptor.vht_info_offset = 0;
- priv->curr_bss_params.bss_descriptor.oper_mode = NULL;
- priv->curr_bss_params.bss_descriptor.oper_mode_offset = 0;
-
- /* Disable 11ac by default. Enable it only where there
- * exist VHT_CAP IE in AP beacon
- */
- priv->curr_bss_params.bss_descriptor.disable_11ac = true;
-
/* Make a copy of current BSSID descriptor */
memcpy(&priv->curr_bss_params.bss_descriptor, bss_desc,
sizeof(priv->curr_bss_params.bss_descriptor));
--
1.7.0.2


2013-04-12 01:01:51

by Troy Kisky

[permalink] [raw]
Subject: Re: [PATCH 2/2] mwifiex: remove redundant initialization for bss_descriptor

On 4/11/2013 5:53 PM, Bing Zhao wrote:
> Initialization of bss_descriptor is unnecessary as the entire
> structure will be overwritten by a memcpy.
>
> Reported-by: Doug Anderson <[email protected]>
> Reviewed-by: Doug Anderson <[email protected]>
> Reviewed-by: Paul Stewart <[email protected]>
> Signed-off-by: Bing Zhao <[email protected]>
> Signed-off-by: Yogesh Ashok Powar <[email protected]>
> ---
> drivers/net/wireless/mwifiex/scan.c | 29 -----------------------------
> 1 files changed, 0 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/net/wireless/mwifiex/scan.c b/drivers/net/wireless/mwifiex/scan.c
> index 37b24e8..9cf5d8f 100644
> --- a/drivers/net/wireless/mwifiex/scan.c
> +++ b/drivers/net/wireless/mwifiex/scan.c
> @@ -1500,36 +1500,7 @@ static int mwifiex_update_curr_bss_params(struct mwifiex_private *priv,
> if (ret)
> goto done;
>
> - /* Update current bss descriptor parameters */
> spin_lock_irqsave(&priv->curr_bcn_buf_lock, flags);
> - priv->curr_bss_params.bss_descriptor.bcn_wpa_ie = NULL;
> - priv->curr_bss_params.bss_descriptor.wpa_offset = 0;
> - priv->curr_bss_params.bss_descriptor.bcn_rsn_ie = NULL;
> - priv->curr_bss_params.bss_descriptor.rsn_offset = 0;
> - priv->curr_bss_params.bss_descriptor.bcn_wapi_ie = NULL;
> - priv->curr_bss_params.bss_descriptor.wapi_offset = 0;
> - priv->curr_bss_params.bss_descriptor.bcn_ht_cap = NULL;
> - priv->curr_bss_params.bss_descriptor.ht_cap_offset = 0;
> - priv->curr_bss_params.bss_descriptor.bcn_ht_oper = NULL;
> - priv->curr_bss_params.bss_descriptor.ht_info_offset = 0;
> - priv->curr_bss_params.bss_descriptor.bcn_bss_co_2040 = NULL;
> - priv->curr_bss_params.bss_descriptor.bss_co_2040_offset = 0;
> - priv->curr_bss_params.bss_descriptor.bcn_ext_cap = NULL;
> - priv->curr_bss_params.bss_descriptor.ext_cap_offset = 0;
> - priv->curr_bss_params.bss_descriptor.beacon_buf = NULL;
> - priv->curr_bss_params.bss_descriptor.beacon_buf_size = 0;
> - priv->curr_bss_params.bss_descriptor.bcn_vht_cap = NULL;
> - priv->curr_bss_params.bss_descriptor.vht_cap_offset = 0;
> - priv->curr_bss_params.bss_descriptor.bcn_vht_oper = NULL;
> - priv->curr_bss_params.bss_descriptor.vht_info_offset = 0;
> - priv->curr_bss_params.bss_descriptor.oper_mode = NULL;
> - priv->curr_bss_params.bss_descriptor.oper_mode_offset = 0;
> -
> - /* Disable 11ac by default. Enable it only where there
> - * exist VHT_CAP IE in AP beacon
> - */
> - priv->curr_bss_params.bss_descriptor.disable_11ac = true;
> -

Should the = true line be moved below the memcpy? Your way produces
the same behavior, but was it buggy before?
> /* Make a copy of current BSSID descriptor */
> memcpy(&priv->curr_bss_params.bss_descriptor, bss_desc,
> sizeof(priv->curr_bss_params.bss_descriptor));


2013-04-12 01:47:01

by Bing Zhao

[permalink] [raw]
Subject: RE: [PATCH 2/2] mwifiex: remove redundant initialization for bss_descriptor

Hi Troy,

Thanks for reviewing.

> > - priv->curr_bss_params.bss_descriptor.disable_11ac = true;
> > -
>
> Should the = true line be moved below the memcpy? Your way produces
> the same behavior, but was it buggy before?

"bss_descriptor.disable_11ac = true" shouldn't be set after memcpy, because bss_desc->disable_11ac reflects the associated AP's 11ac setting here.

Perhaps we should set "bss_desc->disable_11ac = true" earlier before parsing AP's beacon IE?

@@ -184,6 +184,8 @@ int mwifiex_fill_new_bss_desc(struct mwifiex_private *priv,
else
bss_desc->bss_mode = NL80211_IFTYPE_STATION;

+ bss_desc->disable_11ac = true;
+
return mwifiex_update_bss_desc_with_ie(priv->adapter, bss_desc);
}

This flag can be reset to false if AP's beacon does advertise 11ac support.

Yogesh, any thoughts?

We had offline discussion on replacing disable_11ac with existing VHT flags.
Maybe initializing it in mwifiex_fill_new_bss_desc() is way to go?

Thanks,
Bing

> > /* Make a copy of current BSSID descriptor */
> > memcpy(&priv->curr_bss_params.bss_descriptor, bss_desc,
> > sizeof(priv->curr_bss_params.bss_descriptor));