Currently, it is assumed that key_idx values that are passed to
ieee80211_del_key() are all valid indexes as is, and no sanity checks
are performed for it.
However, syzbot was able to trigger an array-index-out-of-bounds bug
by passing a key_idx value of 5, when the maximum permissible index
value is (NUM_DEFAULT_KEYS - 1).
Enforcing sanity checks helps in preventing this bug, or a similar
instance in the context of ieee80211_del_key() from occurring.
Reported-by: [email protected]
Tested-by: [email protected]
Signed-off-by: Anant Thazhemadam <[email protected]>
---
net/mac80211/cfg.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 7276e66ae435..d349e33134e6 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -516,12 +516,30 @@ static int ieee80211_del_key(struct wiphy *wiphy, struct net_device *dev,
if (!sta)
goto out_unlock;
- if (pairwise)
+ if (pairwise) {
+ if (key_idx >= NUM_DEFAULT_KEYS) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
key = key_mtx_dereference(local, sta->ptk[key_idx]);
- else
+ } else {
+ if (key_idx >= (NUM_DEFAULT_KEYS +
+ NUM_DEFAULT_MGMT_KEYS +
+ NUM_DEFAULT_BEACON_KEYS)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
key = key_mtx_dereference(local, sta->gtk[key_idx]);
- } else
+ }
+ } else {
+ if (key_idx >= (NUM_DEFAULT_KEYS +
+ NUM_DEFAULT_MGMT_KEYS +
+ NUM_DEFAULT_BEACON_KEYS)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
key = key_mtx_dereference(local, sdata->keys[key_idx]);
+ }
if (!key) {
ret = -ENOENT;
--
2.25.1
On Tue, 2020-12-01 at 15:26 +0530, Anant Thazhemadam wrote:
> Currently, it is assumed that key_idx values that are passed to
> ieee80211_del_key() are all valid indexes as is, and no sanity checks
> are performed for it.
> However, syzbot was able to trigger an array-index-out-of-bounds bug
> by passing a key_idx value of 5, when the maximum permissible index
> value is (NUM_DEFAULT_KEYS - 1).
> Enforcing sanity checks helps in preventing this bug, or a similar
> instance in the context of ieee80211_del_key() from occurring.
I think we should do this more generally in cfg80211, like in
nl80211_new_key() we do it via cfg80211_validate_key_settings().
I suppose we cannot use the same function, but still, would be good to
address this generally in nl80211 for all drivers.
johannes
On 01/12/20 3:30 pm, Johannes Berg wrote:
> On Tue, 2020-12-01 at 15:26 +0530, Anant Thazhemadam wrote:
>> Currently, it is assumed that key_idx values that are passed to
>> ieee80211_del_key() are all valid indexes as is, and no sanity checks
>> are performed for it.
>> However, syzbot was able to trigger an array-index-out-of-bounds bug
>> by passing a key_idx value of 5, when the maximum permissible index
>> value is (NUM_DEFAULT_KEYS - 1).
>> Enforcing sanity checks helps in preventing this bug, or a similar
>> instance in the context of ieee80211_del_key() from occurring.
> I think we should do this more generally in cfg80211, like in
> nl80211_new_key() we do it via cfg80211_validate_key_settings().
>
> I suppose we cannot use the same function, but still, would be good to
> address this generally in nl80211 for all drivers.
Hello,
This gave me the idea of trying to use cfg80211_validate_key_settings()
directly in ieee80211_del_key(). I did try that out, tested it, and this bug
doesn't seem to be getting triggered anymore.
If this is okay, then I can send in a v2 soon. :)
If there is any reason that I'm missing as to why cfg80211_validate_key_settings()
cannot be used in this context, please let me know.
Thanks,
Anant
On Tue, 2020-12-01 at 17:26 +0530, Anant Thazhemadam wrote:
> On 01/12/20 3:30 pm, Johannes Berg wrote:
> > On Tue, 2020-12-01 at 15:26 +0530, Anant Thazhemadam wrote:
> > > Currently, it is assumed that key_idx values that are passed to
> > > ieee80211_del_key() are all valid indexes as is, and no sanity checks
> > > are performed for it.
> > > However, syzbot was able to trigger an array-index-out-of-bounds bug
> > > by passing a key_idx value of 5, when the maximum permissible index
> > > value is (NUM_DEFAULT_KEYS - 1).
> > > Enforcing sanity checks helps in preventing this bug, or a similar
> > > instance in the context of ieee80211_del_key() from occurring.
> > I think we should do this more generally in cfg80211, like in
> > nl80211_new_key() we do it via cfg80211_validate_key_settings().
> >
> > I suppose we cannot use the same function, but still, would be good to
> > address this generally in nl80211 for all drivers.
>
> Hello,
>
> This gave me the idea of trying to use cfg80211_validate_key_settings()
> directly in ieee80211_del_key(). I did try that out, tested it, and this bug
> doesn't seem to be getting triggered anymore.
> If this is okay, then I can send in a v2 soon. :)
>
> If there is any reason that I'm missing as to why cfg80211_validate_key_settings()
> cannot be used in this context, please let me know.
If it works then I guess that's OK. I thought we didn't have all the
right information, e.g. whether a key is pairwise or not?
johannes
On 01/12/20 5:36 pm, Johannes Berg wrote:
> On Tue, 2020-12-01 at 17:26 +0530, Anant Thazhemadam wrote:
>> On 01/12/20 3:30 pm, Johannes Berg wrote:
>>> On Tue, 2020-12-01 at 15:26 +0530, Anant Thazhemadam wrote:
>>>> Currently, it is assumed that key_idx values that are passed to
>>>> ieee80211_del_key() are all valid indexes as is, and no sanity checks
>>>> are performed for it.
>>>> However, syzbot was able to trigger an array-index-out-of-bounds bug
>>>> by passing a key_idx value of 5, when the maximum permissible index
>>>> value is (NUM_DEFAULT_KEYS - 1).
>>>> Enforcing sanity checks helps in preventing this bug, or a similar
>>>> instance in the context of ieee80211_del_key() from occurring.
>>> I think we should do this more generally in cfg80211, like in
>>> nl80211_new_key() we do it via cfg80211_validate_key_settings().
>>>
>>> I suppose we cannot use the same function, but still, would be good to
>>> address this generally in nl80211 for all drivers.
>> Hello,
>>
>> This gave me the idea of trying to use cfg80211_validate_key_settings()
>> directly in ieee80211_del_key(). I did try that out, tested it, and this bug
>> doesn't seem to be getting triggered anymore.
>> If this is okay, then I can send in a v2 soon. :)
>>
>> If there is any reason that I'm missing as to why cfg80211_validate_key_settings()
>> cannot be used in this context, please let me know.
> If it works then I guess that's OK. I thought we didn't have all the
> right information, e.g. whether a key is pairwise or not?
>
> johannes
>
Well,
cfg80211_supported_cipher_suite(&rdev->wiphy, params->cipher) returned
false, and thus it worked for the syzbot reproducer.
Would it be a safer idea to enforce the conditions that I initially put (in
ieee80211_del_key()) directly in cfg80211_validate_key_settings() itself - by
updating max_key_index, and checking accordingly?
Thanks,
Anant