On 02/08/2012 10:27 AM, Arend van Spriel wrote:
On 02/08/2012 05:08 PM, Felix Fietkau wrote:
On 2012-02-08 1:44 PM, 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.
I'm not sure this is the right fix. If I understand the issue correctly,
mi->r is only NULL because .rate_init has not been called yet, which is
a bug that other rate control modules might trip over as well, maybe in
more subtle ways. If this is the case, then I believe this bug should be
fixed in mac80211 instead.
Maybe it would even be a good idea to set a flag after calling
rate_control_rate_init, and calling WARN_ON or even BUG_ON when doing tx
before that.
- Felix
Hi Felix,
I am not sure I can agree. minstrel_ht allocates the struct
minstrel_ht_sta_priv initializing is_ht to false thereby choosing a
default and zero'ing the legacy field. When setting is_ht to false
consequently the contents of the legacy field should be properly set as
is done in minstrel_ht_update_caps (at use_legacy label).
Once you settle on a "final" patch, I can test it as I can force the crash
nearly instantly.
Larry
--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
