sound/core/hrtimer.c in the Linux kernel before 4.4.1 does not prevent recursive callback access, which allows local users to cause a denial of service (deadlock) via a crafted ioctl call. However, the previous fix is still insufficient: it may still cause a lockup when the ALSA timer instance reprograms itself in its callback. Then it invokes the start function even in snd_timer_interrupt() that is called in hrtimer callback itself, results in a CPU stall. This is no hypothetical problem but actually triggered by syzkaller fuzzer.
jdstrand | android kernels (flo, goldfish, grouper, maguro, mako and manta) are not supported on the Ubuntu Touch 14.10 and earlier preview kernels linux-lts-saucy no longer receives official support linux-lts-quantal no longer receives official support