[v5.4.y,v4.19.y] nl80211: validate key indexes for cfg80211_registered_device

* [v5.4.y,v4.19.y] nl80211: validate key indexes for cfg80211_registered_device
@ 2021-06-03 16:28 Zubin Mithra
  2021-06-04 18:26 ` Sasha Levin
  0 siblings, 1 reply; 2+ messages in thread
From: Zubin Mithra @ 2021-06-03 16:28 UTC (permalink / raw)
  To: stable; +Cc: gregkh, groeck, anant.thazhemadam, johannes.berg

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: Zubin Mithra <zsm@chromium.org>
---
* Syzkaller triggered an OOB-read with the following stacktrace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xef/0x160 lib/dump_stack.c:118
 print_address_description.constprop.0+0x17/0x311 mm/kasan/report.c:374
 __kasan_report+0x145/0x18c mm/kasan/report.c:506
 kasan_report+0x10/0x16 mm/kasan/common.c:634
 ieee80211_key_free+0xb8/0xef net/mac80211/key.c:844
 ieee80211_del_key+0x324/0x354 net/mac80211/cfg.c:532
 rdev_del_key net/wireless/rdev-ops.h:107 [inline]
 nl80211_del_key+0x636/0x758 net/wireless/nl80211.c:4081
 genl_family_rcv_msg+0xaa4/0xbb1 net/netlink/genetlink.c:629
 genl_rcv_msg+0xce/0x127 net/netlink/genetlink.c:654
 netlink_rcv_skb+0x23d/0x318 net/netlink/af_netlink.c:2478
 genl_rcv+0x24/0x31 net/netlink/genetlink.c:665
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x432/0x556 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x943/0x9a8 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:638 [inline]
 sock_sendmsg+0xd5/0x10c net/socket.c:658
 ____sys_sendmsg+0x4ea/0x641 net/socket.c:2298
 ___sys_sendmsg+0x14a/0x1a9 net/socket.c:2352
 __sys_sendmsg+0xf1/0x181 net/socket.c:2398
 do_syscall_64+0x106/0x13f arch/x86/entry/common.c:299
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

* This commit is present in 5.10.y. The crash does not occur
on 4.14.y and older.

* Tests run: syzkaller reproducer, Chrome OS tryjobs

 net/wireless/core.h    |  2 ++
 net/wireless/nl80211.c |  7 ++++---
 net/wireless/util.c    | 39 ++++++++++++++++++++++++++++++++++++++-
 3 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/net/wireless/core.h b/net/wireless/core.h
index d83c8e009448..17621d22fb17 100644
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -433,6 +433,8 @@ void cfg80211_sme_abandon_assoc(struct wireless_dev *wdev);
 
 /* 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);
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 5bb2316befb9..7b170ed6923e 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -3979,9 +3979,6 @@ static int nl80211_del_key(struct sk_buff *skb, struct genl_info *info)
 	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]);
 
@@ -3997,6 +3994,10 @@ static int nl80211_del_key(struct sk_buff *skb, struct genl_info *info)
 	    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;
 
diff --git a/net/wireless/util.c b/net/wireless/util.c
index 82244e2fc1f5..4eae6ad32851 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -229,11 +229,48 @@ bool cfg80211_supported_cipher_suite(struct wiphy *wiphy, u32 cipher)
 	return false;
 }
 
+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;
+
+	if (pairwise)
+		max_key_idx = 3;
+	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 (key_idx < 0 || key_idx > 5)
+	if (!cfg80211_valid_key_idx(rdev, key_idx, pairwise))
 		return -EINVAL;
 
 	if (!pairwise && mac_addr && !(rdev->wiphy.flags & WIPHY_FLAG_IBSS_RSN))
-- 
2.20.0


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