In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: btmtksdio: fix infinite loop in btmtksdio_txrx_work()
Every once in a while we see a hung btmtksdio_flush() task:
INFO: task kworker/u17:0:189 blocked for more than 122 seconds. __cancel_work_timer+0x3f4/0x460 cancel_work_sync+0x1c/0x2c btmtksdio_flush+0x2c/0x40 hci_dev_open_sync+0x10c4/0x2190 [..]
It all boils down to incorrect time_is_before_jiffies() usage in btmtksdio_txrx_work(). The btmtksdio_txrx_work() loop is expected to be terminated if running for longer than 5HZ. However the timeout check is twisted: time_is_before_jiffies(old_jiffies + 5HZ) evaluates to true when old_jiffies + 5*HZ is in the past i.e. when a timeout has occurred. Using OR with time_is_before_jiffies(txrx_timeout) means that:
- before the 5-second timeout: the condition is
int_status || false, so it loops as long as there are pending interrupts. - after the 5-second timeout: the condition becomes
int_status || true, which is always true.
When the loop becomes infinite btmtksdio_txrx_work() loop never terminates and never releases the SDIO host.
Fix loop termination condition to actually enforce a 5*HZ timeout.
References
- https://git.kernel.org/stable/c/0039bdde36b23ccf1196635f1d52c5490481544d
- https://git.kernel.org/stable/c/0f0a83e26a9c7fd4b243c315ce07161d2496d83d
- https://git.kernel.org/stable/c/466540e045d01fcacf383a5beb8a2dad2fc53a26
- https://git.kernel.org/stable/c/7b429d611060e87752e848851815537963726493
- https://git.kernel.org/stable/c/a257407e2bbbb099ed427719a50563f67fa366d8
- https://git.kernel.org/stable/c/f6682c23b6fac4780d297ae4662053d17e58fd52