CVE-2022-49090

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> arch/arm64: Fix topology initialization for core scheduling<br /> <br /> Arm64 systems rely on store_cpu_topology() to call update_siblings_masks()<br /> to transfer the toplogy to the various cpu masks. This needs to be done<br /> before the call to notify_cpu_starting() which tells the scheduler about<br /> each cpu found, otherwise the core scheduling data structures are setup<br /> in a way that does not match the actual topology.<br /> <br /> With smt_mask not setup correctly we bail on `cpumask_weight(smt_mask) == 1`<br /> for !leaders in:<br /> <br /> notify_cpu_starting()<br /> cpuhp_invoke_callback_range()<br /> sched_cpu_starting()<br /> sched_core_cpu_starting()<br /> <br /> which leads to rq-&gt;core not being correctly set for !leader-rq&amp;#39;s.<br /> <br /> Without this change stress-ng (which enables core scheduling in its prctl<br /> tests in newer versions -- i.e. with PR_SCHED_CORE support) causes a warning<br /> and then a crash (trimmed for legibility):<br /> <br /> [ 1853.805168] ------------[ cut here ]------------<br /> [ 1853.809784] task_rq(b)-&gt;core != rq-&gt;core<br /> [ 1853.809792] WARNING: CPU: 117 PID: 0 at kernel/sched/fair.c:11102 cfs_prio_less+0x1b4/0x1c4<br /> ...<br /> [ 1854.015210] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010<br /> ...<br /> [ 1854.231256] Call trace:<br /> [ 1854.233689] pick_next_task+0x3dc/0x81c<br /> [ 1854.237512] __schedule+0x10c/0x4cc<br /> [ 1854.240988] schedule_idle+0x34/0x54