Re: [PATCH v2] mac80211: minstrel_ht: fix NULL pointer dereference during auth/assoc

[Larry Finger <Larry.Finger@lwfinger.net>]

On 02/08/2012 06:44 AM, Arend van Spriel wrote:
> This patch fixes the following NULL pointer dereference:
>
>> I rerun the test on a kernel with some more lock checking and got lucky.
>>
>> Feb  8 08:40:17 lb-bun-10 kernel: [  514.512283] wlan0: authenticate
>> with 98:fc:11:8e:94:57
>> Feb  8 08:40:17 lb-bun-10 kernel: [  514.512515] wlan0: send auth to
>> 98:fc:11:8e:94:57 (try 1/3)
>> Feb  8 08:40:17 lb-bun-10 kernel: [  514.514184] BUG: unable to handle
>> kernel NULL pointer dereference at 00000004
>> Feb  8 08:40:17 lb-bun-10 kernel: [  514.514233] IP: [<f8648f08>]
>> minstrel_tx_status+0x48/0xe0 [mac80211]
>
> static inline int
> rix_to_ndx(struct minstrel_sta_info *mi, int rix)
> {
>          int i = rix;
>          for (i = rix; i>= 0; i--)
>                  if (mi->r[i].rix == rix)
>    48:   3b 58 04                cmp    0x4(%eax),%ebx
>    4b:   74 4b                   je     98<minstrel_tx_status+0x98>
>    4d:   83 c2 01                add    $0x1,%edx
>
> It fails because of mi->r[i] being a NULL pointer. It is allocated in
> minstel_alloc_sta, but minstrel_ht_alloc_sta does not call that function.
>
> struct minstrel_ht_sta_priv holds a union with struct minstrel_ht_sta and
> struct minstrel_sta_info. During authenticate the bool is_ht is false so
> minstrel_ht_tx_status calls minstrel_tx_status, but minstrel_sta_info::r
> is not set until rate_init which is after assoc.
>
> Cc: Johannes Berg<johannes@sipsolutions.net>
> Cc: Felix Fietkau<nbd@openwrt.org>
> Signed-off-by: Arend van Spriel<arend@broadcom.com>
> ---
> John,
>
> This one with tab indent instead of spaces. Noticed just after sending
> the first patch.
>
> Gr. AvS
> ---
>   net/mac80211/rc80211_minstrel_ht.c |    3 +++
>   1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/net/mac80211/rc80211_minstrel_ht.c b/net/mac80211/rc80211_minstrel_ht.c
> index ff5f7b8..a58c348 100644
> --- a/net/mac80211/rc80211_minstrel_ht.c
> +++ b/net/mac80211/rc80211_minstrel_ht.c
> @@ -813,6 +813,9 @@ minstrel_ht_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
>   	if (!msp->sample_table)
>   		goto error1;
>
> +	msp->legacy.r = msp->ratelist;
> +	msp->legacy.sample_table = msp->sample_table;
> +
>   	return msp;
>
>   error1:

This patch fixes the problem I was having with minstrel_tx_status with p54usb.

John: If you want, you may add a

Tested-by: Larry Finger <Larry.Finger@lwfinger.net>

Arend: Thanks for finding this problem and fixing it.

Larry