From: Waiman Long longman@redhat.com
[ Upstream commit b6e8d40d43ae4dec00c8fea2593eeea3114b8f44 ]
With cgroup v2, the cpuset's cpus_allowed mask can be empty indicating that the cpuset will just use the effective CPUs of its parent. So cpuset_can_attach() can call task_can_attach() with an empty mask. This can lead to cpumask_any_and() returns nr_cpu_ids causing the call to dl_bw_of() to crash due to percpu value access of an out of bound CPU value. For example:
[80468.182258] BUG: unable to handle page fault for address: ffffffff8b6648b0 : [80468.191019] RIP: 0010:dl_cpu_busy+0x30/0x2b0 : [80468.207946] Call Trace: [80468.208947] cpuset_can_attach+0xa0/0x140 [80468.209953] cgroup_migrate_execute+0x8c/0x490 [80468.210931] cgroup_update_dfl_csses+0x254/0x270 [80468.211898] cgroup_subtree_control_write+0x322/0x400 [80468.212854] kernfs_fop_write_iter+0x11c/0x1b0 [80468.213777] new_sync_write+0x11f/0x1b0 [80468.214689] vfs_write+0x1eb/0x280 [80468.215592] ksys_write+0x5f/0xe0 [80468.216463] do_syscall_64+0x5c/0x80 [80468.224287] entry_SYSCALL_64_after_hwframe+0x44/0xae
Fix that by using effective_cpus instead. For cgroup v1, effective_cpus is the same as cpus_allowed. For v2, effective_cpus is the real cpumask to be used by tasks within the cpuset anyway.
Also update task_can_attach()'s 2nd argument name to cs_effective_cpus to reflect the change. In addition, a check is added to task_can_attach() to guard against the possibility that cpumask_any_and() may return a value >= nr_cpu_ids.
Fixes: 7f51412a415d ("sched/deadline: Fix bandwidth check/update when migrating tasks between exclusive cpusets") Signed-off-by: Waiman Long longman@redhat.com Signed-off-by: Ingo Molnar mingo@kernel.org Acked-by: Juri Lelli juri.lelli@redhat.com Link: https://lore.kernel.org/r/20220803015451.2219567-1-longman@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/sched.h | 2 +- kernel/cgroup/cpuset.c | 2 +- kernel/sched/core.c | 8 +++++--- 3 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h index ad7ff332a0ac..dcba347cbffa 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1797,7 +1797,7 @@ current_restore_flags(unsigned long orig_flags, unsigned long flags) }
extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial); -extern int task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed); +extern int task_can_attach(struct task_struct *p, const struct cpumask *cs_effective_cpus); #ifdef CONFIG_SMP extern void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask); extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask); diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 31f94c6ea0a5..9c5b659db63f 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2199,7 +2199,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) goto out_unlock;
cgroup_taskset_for_each(task, css, tset) { - ret = task_can_attach(task, cs->cpus_allowed); + ret = task_can_attach(task, cs->effective_cpus); if (ret) goto out_unlock; ret = security_task_setscheduler(task); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 154506e4d1f5..5c7937b504d2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8741,7 +8741,7 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur, }
int task_can_attach(struct task_struct *p, - const struct cpumask *cs_cpus_allowed) + const struct cpumask *cs_effective_cpus) { int ret = 0;
@@ -8760,9 +8760,11 @@ int task_can_attach(struct task_struct *p, }
if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span, - cs_cpus_allowed)) { - int cpu = cpumask_any_and(cpu_active_mask, cs_cpus_allowed); + cs_effective_cpus)) { + int cpu = cpumask_any_and(cpu_active_mask, cs_effective_cpus);
+ if (unlikely(cpu >= nr_cpu_ids)) + return -EINVAL; ret = dl_cpu_busy(cpu, p); }