mac802154: Fix potential RCU dereference issue in mac802154_scan_worker

In the `mac802154_scan_worker` function, the `scan_req->type` field was
accessed after the RCU read-side critical section was unlocked. According
to RCU usage rules, this is illegal and can lead to unpredictable
behavior, such as accessing memory that has been updated or causing
use-after-free issues.

This possible bug was identified using a static analysis tool developed
by myself, specifically designed to detect RCU-related issues.

To address this, the `scan_req->type` value is now stored in a local
variable `scan_req_type` while still within the RCU read-side critical
section. The `scan_req_type` is then used after the RCU lock is released,
ensuring that the type value is safely accessed without violating RCU
rules.

Fixes: e2c3e6f53a7a ("mac802154: Handle active scanning")
Cc: stable@vger.kernel.org
Signed-off-by: Jiawei Ye <jiawei.ye@foxmail.com>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://lore.kernel.org/tencent_3B2F4F2B4DA30FAE2F51A9634A16B3AD4908@qq.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

diff --git a/net/mac802154/scan.c b/net/mac802154/scan.c
index 1c0eeaa76560cdf0e533aad07fe6e555a0687f6d..a6dab3cc3ad85823e9000ecdc1a62415d3fb248a 100644 (file)
--- a/net/mac802154/scan.c
+++ b/net/mac802154/scan.c
@@ -176,6 +176,7 @@ void mac802154_scan_worker(struct work_struct *work)
        struct ieee802154_local *local =
                container_of(work, struct ieee802154_local, scan_work.work);
        struct cfg802154_scan_request *scan_req;
+       enum nl802154_scan_types scan_req_type;
        struct ieee802154_sub_if_data *sdata;
        unsigned int scan_duration = 0;
        struct wpan_phy *wpan_phy;
@@ -209,6 +210,7 @@ void mac802154_scan_worker(struct work_struct *work)
        }
 
        wpan_phy = scan_req->wpan_phy;
+       scan_req_type = scan_req->type;
        scan_req_duration = scan_req->duration;
 
        /* Look for the next valid chan */
@@ -246,7 +248,7 @@ void mac802154_scan_worker(struct work_struct *work)
                goto end_scan;
        }
 
-       if (scan_req->type == NL802154_SCAN_ACTIVE) {
+       if (scan_req_type == NL802154_SCAN_ACTIVE) {
                ret = mac802154_transmit_beacon_req(local, sdata);
                if (ret)
                        dev_err(&sdata->dev->dev,