2012-07-09 16:49:47

by Arik Nemtsov

Subject: [PATCH] mac80211: fix invalid band deref building preq IEs

The function building probe-request IEs does not validate the band is
supported before dereferencing it. This can result in a panic when
all bands are traversed, as done during sched-scan start.

Warn when this happens and return an empty probe request. Also fix
sched-scan to not waste memory on unsupported bands.

Signed-off-by: Arik Nemtsov <[email protected]>
---
This is not cc stable since the panic only started happening once
the 60Ghz band was added. Apparently all sched-scan drivers supported
all possible bands until then.


net/mac80211/scan.c | 3 +++
net/mac80211/util.c | 2 ++
2 files changed, 5 insertions(+)

diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 379f178..1ff04f6 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -928,6 +928,9 @@ int ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
}

for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
+ if (!local->hw.wiphy->bands[i])
+ continue;
+
local->sched_scan_ies.ie[i] = kzalloc(2 +
IEEE80211_MAX_SSID_LEN +
local->scan_ies_len +
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 64493a7..503412a 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -999,6 +999,8 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
int ext_rates_len;

sband = local->hw.wiphy->bands[band];
+ if (!WARN_ON_ONCE(sband))
+ return 0;

pos = buffer;

--
1.7.9.5

2012-07-09 16:55:29

by Arik Nemtsov

Subject: Re: [PATCH] mac80211: fix invalid band deref building preq IEs

On Mon, Jul 9, 2012 at 7:54 PM, Johannes Berg <[email protected]> wrote:
> On Mon, 2012-07-09 at 19:49 +0300, Arik Nemtsov wrote:
>> The function building probe-request IEs does not validate the band is
>> supported before dereferencing it. This can result in a panic when
>> all bands are traversed, as done during sched-scan start.
>>
>> Warn when this happens and return an empty probe request. Also fix
>> sched-scan to not waste memory on unsupported bands.
>>
>> Signed-off-by: Arik Nemtsov <[email protected]>
>> ---
>> This is not cc stable since the panic only started happening once
>> the 60Ghz band was added. Apparently all sched-scan drivers supported
>> all possible bands until then.
>>
>>
>> net/mac80211/scan.c | 3 +++
>> net/mac80211/util.c | 2 ++
>> 2 files changed, 5 insertions(+)
>>
>> diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
>> index 379f178..1ff04f6 100644
>> --- a/net/mac80211/scan.c
>> +++ b/net/mac80211/scan.c
>> @@ -928,6 +928,9 @@ int ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
>> }
>>
>> for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
>> + if (!local->hw.wiphy->bands[i])
>> + continue;
>> +
>> local->sched_scan_ies.ie[i] = kzalloc(2 +
>> IEEE80211_MAX_SSID_LEN +
>> local->scan_ies_len +
>> diff --git a/net/mac80211/util.c b/net/mac80211/util.c
>> index 64493a7..503412a 100644
>> --- a/net/mac80211/util.c
>> +++ b/net/mac80211/util.c
>> @@ -999,6 +999,8 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
>> int ext_rates_len;
>>
>> sband = local->hw.wiphy->bands[band];
>> + if (!WARN_ON_ONCE(sband))
>> + return 0;
>
> That's not right :-)

heh. yea I guess I didn't test it with the WARN_ON :)

2012-07-09 16:54:04

by Johannes Berg

Subject: Re: [PATCH] mac80211: fix invalid band deref building preq IEs

On Mon, 2012-07-09 at 19:49 +0300, Arik Nemtsov wrote:
> The function building probe-request IEs does not validate the band is
> supported before dereferencing it. This can result in a panic when
> all bands are traversed, as done during sched-scan start.
>
> Warn when this happens and return an empty probe request. Also fix
> sched-scan to not waste memory on unsupported bands.
>
> Signed-off-by: Arik Nemtsov <[email protected]>
> ---
> This is not cc stable since the panic only started happening once
> the 60Ghz band was added. Apparently all sched-scan drivers supported
> all possible bands until then.
>
>
> net/mac80211/scan.c | 3 +++
> net/mac80211/util.c | 2 ++
> 2 files changed, 5 insertions(+)
>
> diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
> index 379f178..1ff04f6 100644
> --- a/net/mac80211/scan.c
> +++ b/net/mac80211/scan.c
> @@ -928,6 +928,9 @@ int ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
> }
>
> for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
> + if (!local->hw.wiphy->bands[i])
> + continue;
> +
> local->sched_scan_ies.ie[i] = kzalloc(2 +
> IEEE80211_MAX_SSID_LEN +
> local->scan_ies_len +
> diff --git a/net/mac80211/util.c b/net/mac80211/util.c
> index 64493a7..503412a 100644
> --- a/net/mac80211/util.c
> +++ b/net/mac80211/util.c
> @@ -999,6 +999,8 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
> int ext_rates_len;
>
> sband = local->hw.wiphy->bands[band];
> + if (!WARN_ON_ONCE(sband))
> + return 0;

That's not right :-)

johannes