[PATCH 3.11] mac80211/minstrel: fix NULL pointer dereference issue

[PATCH 3.11] mac80211/minstrel: fix NULL pointer dereference issue

[Felix Fietkau]

When priv_sta == NULL, mi->prev_sample is dereferenced too early. Move
the assignment further down, after the rate_control_send_low call.

Reported-by: Krzysztof Mazur <krzysiek@podlesie.net>
Cc: stable@vger.kernel.org # 3.10
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
---
 net/mac80211/rc80211_minstrel.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index ac7ef54..e6512e2 100644
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -290,7 +290,7 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
 	struct minstrel_rate *msr, *mr;
 	unsigned int ndx;
 	bool mrr_capable;
-	bool prev_sample = mi->prev_sample;
+	bool prev_sample;
 	int delta;
 	int sampling_ratio;
 
@@ -314,6 +314,7 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
 			(mi->sample_count + mi->sample_deferred / 2);
 
 	/* delta < 0: no sampling required */
+	prev_sample = mi->prev_sample;
 	mi->prev_sample = false;
 	if (delta < 0 || (!mrr_capable && prev_sample))
 		return;
-- 
1.8.0.2

Re: [PATCH 3.11] mac80211/minstrel: fix NULL pointer dereference issue

[Joe Perches]

On Mon, 2013-07-15 at 14:35 +0200, Felix Fietkau wrote:
> When priv_sta == NULL, mi->prev_sample is dereferenced too early. Move
> the assignment further down, after the rate_control_send_low call.
> 
> Reported-by: Krzysztof Mazur <krzysiek@podlesie.net>
> Cc: stable@vger.kernel.org # 3.10
> Signed-off-by: Felix Fietkau <nbd@openwrt.org>

Why should this be marked for stable?

It's a local reference only, it's not used.

It's like suggesting that all the initialized
automatics should not be set until after
rate_control_set_low is called.

> ---
>  net/mac80211/rc80211_minstrel.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
> index ac7ef54..e6512e2 100644
> --- a/net/mac80211/rc80211_minstrel.c
> +++ b/net/mac80211/rc80211_minstrel.c
> @@ -290,7 +290,7 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
>  	struct minstrel_rate *msr, *mr;
>  	unsigned int ndx;
>  	bool mrr_capable;
> -	bool prev_sample = mi->prev_sample;
> +	bool prev_sample;
>  	int delta;
>  	int sampling_ratio;
>  
> @@ -314,6 +314,7 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
>  			(mi->sample_count + mi->sample_deferred / 2);
>  
>  	/* delta < 0: no sampling required */
> +	prev_sample = mi->prev_sample;
>  	mi->prev_sample = false;
>  	if (delta < 0 || (!mrr_capable && prev_sample))
>  		return;

Re: [PATCH 3.11] mac80211/minstrel: fix NULL pointer dereference issue

[Felix Fietkau]

On 2013-07-15 2:50 PM, Joe Perches wrote:
> On Mon, 2013-07-15 at 14:35 +0200, Felix Fietkau wrote:
>> When priv_sta == NULL, mi->prev_sample is dereferenced too early. Move
>> the assignment further down, after the rate_control_send_low call.
>> 
>> Reported-by: Krzysztof Mazur <krzysiek@podlesie.net>
>> Cc: stable@vger.kernel.org # 3.10
>> Signed-off-by: Felix Fietkau <nbd@openwrt.org>
> 
> Why should this be marked for stable?
> 
> It's a local reference only, it's not used.
> 
> It's like suggesting that all the initialized
> automatics should not be set until after
> rate_control_set_low is called.
mi is set to priv_sta. It can be NULL. The case of priv_sta==NULL is
caught by rate_control_send_low and causes it to bail out.

- Felix

Re: [PATCH 3.11] mac80211/minstrel: fix NULL pointer dereference issue

[Joe Perches]

On Mon, 2013-07-15 at 14:54 +0200, Felix Fietkau wrote:
> On 2013-07-15 2:50 PM, Joe Perches wrote:
> > On Mon, 2013-07-15 at 14:35 +0200, Felix Fietkau wrote:
> >> When priv_sta == NULL, mi->prev_sample is dereferenced too early. Move
> >> the assignment further down, after the rate_control_send_low call.
[]
> mi is set to priv_sta. It can be NULL. The case of priv_sta==NULL is
> caught by rate_control_send_low and causes it to bail out.

OK, thanks.

Re: [PATCH 3.11] mac80211/minstrel: fix NULL pointer dereference issue

[Krzysztof Mazur]

On Mon, Jul 15, 2013 at 02:35:06PM +0200, Felix Fietkau wrote:
> When priv_sta == NULL, mi->prev_sample is dereferenced too early. Move
> the assignment further down, after the rate_control_send_low call.
> 
> Reported-by: Krzysztof Mazur <krzysiek@podlesie.net>
> Cc: stable@vger.kernel.org # 3.10
> Signed-off-by: Felix Fietkau <nbd@openwrt.org>
> ---
>  net/mac80211/rc80211_minstrel.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Works for me.

Thanks,
Krzysiek

Re: [PATCH 3.11] mac80211/minstrel: fix NULL pointer dereference issue

[Johannes Berg]

On 2013-07-15 15:35, Felix Fietkau wrote:
> When priv_sta == NULL, mi->prev_sample is dereferenced too early. Move
> the assignment further down, after the rate_control_send_low call.

Applied.

johannes