[PATCH 5.10 39/40] nl80211: validate key indexes for cfg80211_registered_device

Greg Kroah-Hartman
2020-12-23T15:34:59Z

From: Anant Thazhemadam <anant.thazhemadam@gmail.com>

commit 2d9463083ce92636a1bdd3e30d1236e3e95d859e upstream.

syzbot discovered a bug in which an OOB access was being made because
an unsuitable key_idx value was wrongly considered to be acceptable
while deleting a key in nl80211_del_key().

Since we don't know the cipher at the time of deletion, if
cfg80211_validate_key_settings() were to be called directly in
nl80211_del_key(), even valid keys would be wrongly determined invalid,
and deletion wouldn't occur correctly.
For this reason, a new function - cfg80211_valid_key_idx(), has been
created, to determine if the key_idx value provided is valid or not.
cfg80211_valid_key_idx() is directly called in 2 places -
nl80211_del_key(), and cfg80211_validate_key_settings().

Reported-by: syzbot+49d4cab497c2142ee170@syzkaller.appspotmail.com
Tested-by: syzbot+49d4cab497c2142ee170@syzkaller.appspotmail.com
Suggested-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
Link: https://lore.kernel.org/r/20201204215825.129879-1-anant.thazhemadam@gmail.com
Cc: stable@vger.kernel.org
[also disallow IGTK key IDs if no IGTK cipher is supported]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/wireless/core.h | 2 +
net/wireless/nl80211.c | 7 +++---
net/wireless/util.c | 51 +++++++++++++++++++++++++++++++++++++++++--------
3 files changed, 49 insertions(+), 11 deletions(-)

--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -433,6 +433,8 @@ void cfg80211_sme_abandon_assoc(struct w

/* internal helpers */
bool cfg80211_supported_cipher_suite(struct wiphy *wiphy, u32 cipher);
+bool cfg80211_valid_key_idx(struct cfg80211_registered_device *rdev,
+ int key_idx, bool pairwise);
int cfg80211_validate_key_settings(struct cfg80211_registered_device *rdev,
struct key_params *params, int key_idx,
bool pairwise, const u8 *mac_addr);
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -4260,9 +4260,6 @@ static int nl80211_del_key(struct sk_buf
if (err)
return err;

- if (key.idx < 0)
- return -EINVAL;
-
if (info->attrs[NL80211_ATTR_MAC])
mac_addr = nla_data(info->attrs[NL80211_ATTR_MAC]);

@@ -4278,6 +4275,10 @@ static int nl80211_del_key(struct sk_buf
key.type != NL80211_KEYTYPE_GROUP)
return -EINVAL;

+ if (!cfg80211_valid_key_idx(rdev, key.idx,
+ key.type == NL80211_KEYTYPE_PAIRWISE))
+ return -EINVAL;
+
if (!rdev->ops->del_key)
return -EOPNOTSUPP;

--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -272,18 +272,53 @@ bool cfg80211_supported_cipher_suite(str
return false;
}

-int cfg80211_validate_key_settings(struct cfg80211_registered_device *rdev,
- struct key_params *params, int key_idx,
- bool pairwise, const u8 *mac_addr)
+static bool
+cfg80211_igtk_cipher_supported(struct cfg80211_registered_device *rdev)
+{
+ struct wiphy *wiphy = &rdev->wiphy;
+ int i;
+
+ for (i = 0; i < wiphy->n_cipher_suites; i++) {
+ switch (wiphy->cipher_suites[i]) {
+ case WLAN_CIPHER_SUITE_AES_CMAC:
+ case WLAN_CIPHER_SUITE_BIP_CMAC_256:
+ case WLAN_CIPHER_SUITE_BIP_GMAC_128:
+ case WLAN_CIPHER_SUITE_BIP_GMAC_256:
+ return true;
+ }
+ }
+
+ return false;
+}
+
+bool cfg80211_valid_key_idx(struct cfg80211_registered_device *rdev,
+ int key_idx, bool pairwise)
{
- int max_key_idx = 5;
+ int max_key_idx;

- if (wiphy_ext_feature_isset(&rdev->wiphy,
- NL80211_EXT_FEATURE_BEACON_PROTECTION) ||
- wiphy_ext_feature_isset(&rdev->wiphy,
- NL80211_EXT_FEATURE_BEACON_PROTECTION_CLIENT))
+ if (pairwise)
+ max_key_idx = 3;
+ else if (wiphy_ext_feature_isset(&rdev->wiphy,
+ NL80211_EXT_FEATURE_BEACON_PROTECTION) ||
+ wiphy_ext_feature_isset(&rdev->wiphy,
+ NL80211_EXT_FEATURE_BEACON_PROTECTION_CLIENT))
max_key_idx = 7;
+ else if (cfg80211_igtk_cipher_supported(rdev))
+ max_key_idx = 5;
+ else
+ max_key_idx = 3;
+
if (key_idx < 0 || key_idx > max_key_idx)
+ return false;
+
+ return true;
+}
+
+int cfg80211_validate_key_settings(struct cfg80211_registered_device *rdev,
+ struct key_params *params, int key_idx,
+ bool pairwise, const u8 *mac_addr)
+{
+ if (!cfg80211_valid_key_idx(rdev, key_idx, pairwise))
return -EINVAL;

if (!pairwise && mac_addr && !(rdev->wiphy.flags & WIPHY_FLAG_IBSS_RSN))