From: Gui-Dong Han
Sent: 22 December 2023 10:55
In {conn,adv}_min_interval_set(): if (val < ... || val > ... || val > hdev->le_{conn,adv}_max_interval) return -EINVAL; hci_dev_lock(hdev); hdev->le_{conn,adv}_min_interval = val; hci_dev_unlock(hdev);
In {conn,adv}_max_interval_set(): if (val < ... || val > ... || val < hdev->le_{conn,adv}_min_interval) return -EINVAL; hci_dev_lock(hdev); hdev->le_{conn,adv}_max_interval hci_dev_unlock(hdev);
The atomicity violation occurs due to concurrent execution of set_min and set_max funcs which may lead to inconsistent reads and writes of the min value and the max value. The checks for value validity are ineffective as the min/max values could change immediately after being checked, raising the risk of the min value being greater than the max value and causing invalid settings.
This possible bug is found by an experimental static analysis tool developed by our team, BassCheck[1]. This tool analyzes the locking APIs to extract function pairs that can be concurrently executed, and then analyzes the instructions in the paired functions to identify possible concurrency bugs including data races and atomicity violations. The above possible bug is reported when our tool analyzes the source code of Linux 5.17.
Your static analysis tool is basically broken.
The only possible issues are if the accesses aren't atomic. In practise they always will be but using READ_ONCE() and WRITE_ONCE() would make that certain.
The lock sequence:
hci_dev_lock(hdev); hdev->le_conn_min_interval = val; hci_dev_unlock(hdev);
is pretty pointless - is doesn't 'lock' two+ things together.
David
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