2011-11-28 21:47:23

by Luis R. Rodriguez

Subject: [PATCH v3 1/2] cfg80211: fix race on init and driver registration

There is a theoretical race that if hit will trigger
a crash. The race is between when we issue the first
regulatory hint, regulatory_hint_core(), gets processed
by the workqueue and between when the first device
gets registered to the wireless core. This is not easy
to reproduce but it was easy to do so through the
regulatory simulator I have been working on. This
is a port of the fix I implemented there [1].

[1] https://github.com/mcgrof/regsim/commit/a246ccf81f059cb662eee288aa13100f631e4cc8

Cc: [email protected]
Cc: Johannes Berg <[email protected]>
Signed-off-by: Luis R. Rodriguez <[email protected]>
---
net/wireless/reg.c | 43 +++++++++++++++++++++++++++----------------
1 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index 76b35df..a5f0ac7 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -57,8 +57,17 @@
#define REG_DBG_PRINT(args...)
#endif

+static struct regulatory_request core_request_world = {
+ .initiator = NL80211_REGDOM_SET_BY_CORE,
+ .alpha2[0] = '0',
+ .alpha2[1] = '0',
+ .intersect = false,
+ .processed = true,
+ .country_ie_env = ENVIRON_ANY,
+};
+
/* Receipt of information from last regulatory request */
-static struct regulatory_request *last_request;
+static struct regulatory_request *last_request = &core_request_world;

/* To trigger userspace events */
static struct platform_device *reg_pdev;
@@ -150,7 +159,7 @@ static char user_alpha2[2];
module_param(ieee80211_regdom, charp, 0444);
MODULE_PARM_DESC(ieee80211_regdom, "IEEE 802.11 regulatory domain code");

-static void reset_regdomains(void)
+static void reset_regdomains(bool full_reset)
{
/* avoid freeing static information or freeing something twice */
if (cfg80211_regdomain == cfg80211_world_regdom)
@@ -165,6 +174,13 @@ static void reset_regdomains(void)

cfg80211_world_regdom = &world_regdom;
cfg80211_regdomain = NULL;
+
+ if (!full_reset)
+ return;
+
+ if (last_request != &core_request_world)
+ kfree(last_request);
+ last_request = &core_request_world;
}

/*
@@ -175,7 +191,7 @@ static void update_world_regdomain(const struct ieee80211_regdomain *rd)
{
BUG_ON(!last_request);

- reset_regdomains();
+ reset_regdomains(false);

cfg80211_world_regdom = rd;
cfg80211_regdomain = rd;
@@ -1409,7 +1425,8 @@ static int __regulatory_hint(struct wiphy *wiphy,
}

new_request:
- kfree(last_request);
+ if (last_request != &core_request_world)
+ kfree(last_request);

last_request = pending_request;
last_request->intersect = intersect;
@@ -1579,9 +1596,6 @@ static int regulatory_hint_core(const char *alpha2)
{
struct regulatory_request *request;

- kfree(last_request);
- last_request = NULL;
-
request = kzalloc(sizeof(struct regulatory_request),
GFP_KERNEL);
if (!request)
@@ -1779,7 +1793,7 @@ static void restore_regulatory_settings(bool reset_user)
mutex_lock(&cfg80211_mutex);
mutex_lock(&reg_mutex);

- reset_regdomains();
+ reset_regdomains(true);
restore_alpha2(alpha2, reset_user);

/*
@@ -2085,7 +2099,7 @@ static int __set_regdom(const struct ieee80211_regdomain *rd)
int r;

if (last_request->initiator != NL80211_REGDOM_SET_BY_DRIVER) {
- reset_regdomains();
+ reset_regdomains(false);
cfg80211_regdomain = rd;
return 0;
}
@@ -2106,7 +2120,7 @@ static int __set_regdom(const struct ieee80211_regdomain *rd)
if (r)
return r;

- reset_regdomains();
+ reset_regdomains(false);
cfg80211_regdomain = rd;
return 0;
}
@@ -2131,7 +2145,7 @@ static int __set_regdom(const struct ieee80211_regdomain *rd)

rd = NULL;

- reset_regdomains();
+ reset_regdomains(false);
cfg80211_regdomain = intersected_rd;

return 0;
@@ -2151,7 +2165,7 @@ static int __set_regdom(const struct ieee80211_regdomain *rd)
kfree(rd);
rd = NULL;

- reset_regdomains();
+ reset_regdomains(false);
cfg80211_regdomain = intersected_rd;

return 0;
@@ -2304,11 +2318,8 @@ void /* __init_or_exit */ regulatory_exit(void)
mutex_lock(&cfg80211_mutex);
mutex_lock(&reg_mutex);

- reset_regdomains();
-
- kfree(last_request);
+ reset_regdomains(true);

- last_request = NULL;
dev_set_uevent_suppress(&reg_pdev->dev, true);

platform_device_unregister(reg_pdev);
--
1.7.4.15.g7811d

2011-11-29 08:41:10

by Johannes Berg

Subject: Re: [PATCH v3 2/2] cfg80211: amend regulatory NULL dereference fix

On Mon, 2011-11-28 at 16:47 -0500, Luis R. Rodriguez wrote:
> Johannes' patch for "cfg80211: fix regulatory NULL dereference"
> broke user regulaotry hints and it did not address the fact that
> last_request was left populated even if the previous regulatory
> hint was stale due to the wiphy disappearing.
>
> Fix user reguluatory hints by only bailing out if for those
> regulatory hints where a request_wiphy is expected. The stale last_request
> considerations are addressed through the previous fixes on last_request
> where we reset the last_request to a static world regdom request upon
> reset_regdomains(). In this case though we further enhance the effect
> by simply restoring reguluatory settings completely.
>
> Cc: [email protected]
> Cc: Johannes Berg <[email protected]>
> Signed-off-by: Luis R. Rodriguez <[email protected]>

Reviewed-by: Johannes Berg <[email protected]>

> ---
> net/wireless/reg.c | 6 ++++--
> 1 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/wireless/reg.c b/net/wireless/reg.c
> index a5f0ac7..70b171a 100644
> --- a/net/wireless/reg.c
> +++ b/net/wireless/reg.c
> @@ -2090,8 +2090,10 @@ static int __set_regdom(const struct ieee80211_regdomain *rd)
> }
>
> request_wiphy = wiphy_idx_to_wiphy(last_request->wiphy_idx);
> - if (!request_wiphy) {
> - reg_set_request_processed();
> + if (!request_wiphy &&
> + (last_request->initiator == NL80211_REGDOM_SET_BY_DRIVER ||
> + last_request->initiator == NL80211_REGDOM_SET_BY_COUNTRY_IE)) {
> + schedule_delayed_work(&reg_timeout, 0);
> return -ENODEV;
> }
>

2011-11-28 21:47:24

by Luis R. Rodriguez

Subject: [PATCH v3 2/2] cfg80211: amend regulatory NULL dereference fix

Johannes' patch for "cfg80211: fix regulatory NULL dereference"
broke user regulaotry hints and it did not address the fact that
last_request was left populated even if the previous regulatory
hint was stale due to the wiphy disappearing.

Fix user reguluatory hints by only bailing out if for those
regulatory hints where a request_wiphy is expected. The stale last_request
considerations are addressed through the previous fixes on last_request
where we reset the last_request to a static world regdom request upon
reset_regdomains(). In this case though we further enhance the effect
by simply restoring reguluatory settings completely.

Cc: [email protected]
Cc: Johannes Berg <[email protected]>
Signed-off-by: Luis R. Rodriguez <[email protected]>
---
net/wireless/reg.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index a5f0ac7..70b171a 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -2090,8 +2090,10 @@ static int __set_regdom(const struct ieee80211_regdomain *rd)
}

request_wiphy = wiphy_idx_to_wiphy(last_request->wiphy_idx);
- if (!request_wiphy) {
- reg_set_request_processed();
+ if (!request_wiphy &&
+ (last_request->initiator == NL80211_REGDOM_SET_BY_DRIVER ||
+ last_request->initiator == NL80211_REGDOM_SET_BY_COUNTRY_IE)) {
+ schedule_delayed_work(&reg_timeout, 0);
return -ENODEV;
}

--
1.7.4.15.g7811d