On 9/19/24 09:16, Jiawei Ye wrote:
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")
Signed-off-by: Jiawei Ye <jiawei.ye@xxxxxxxxxxx>
---
net/mac802154/scan.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/mac802154/scan.c b/net/mac802154/scan.c
index 1c0eeaa76560..29cd84c9f69c 100644
--- a/net/mac802154/scan.c
+++ b/net/mac802154/scan.c
@@ -180,6 +180,7 @@ void mac802154_scan_worker(struct work_struct *work)
unsigned int scan_duration = 0;
struct wpan_phy *wpan_phy;
u8 scan_req_duration;
+ enum nl802154_scan_types scan_req_type;
this line violates the reverse X-mass tree rule of code formatting
u8 page, channel;
int ret;
@@ -210,6 +211,7 @@ void mac802154_scan_worker(struct work_struct *work)
wpan_phy = scan_req->wpan_phy;
this line (not yours) just saves the first level of pointer, but then
accesses wpan_phy->... outside of the rcu_read_lock() section, for me
it's very similar case to what you are fixing here
scan_req_duration = scan_req->duration;
+ scan_req_type = scan_req->type;
/* Look for the next valid chan */
page = local->scan_page;
@@ -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,
