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sched: Split the guts of sched_setaffinity() into a helper function

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In preparation for replaying user affinity requests using a saved mask,
split sched_setaffinity() up so that the initial task lookup and
security checks are only performed when the request is coming directly
from userspace.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lore.kernel.org/r/20210730112443.23245-8-will@kernel.org
This commit is contained in:
Will Deacon 2021-07-30 12:24:34 +01:00 committed by Peter Zijlstra
parent b90ca8badb
commit db3b02ae89
1 changed files with 57 additions and 48 deletions
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105
kernel/sched/core.c
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@ -7594,53 +7594,22 @@ out_unlock:
return retval;
}
long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
static int
__sched_setaffinity(struct task_struct *p, const struct cpumask *mask)
{
cpumask_var_t cpus_allowed, new_mask;
struct task_struct *p;
int retval;
cpumask_var_t cpus_allowed, new_mask;
rcu_read_lock();
if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL))
return -ENOMEM;
p = find_process_by_pid(pid);
if (!p) {
rcu_read_unlock();
return -ESRCH;
}
/* Prevent p going away */
get_task_struct(p);
rcu_read_unlock();
if (p->flags & PF_NO_SETAFFINITY) {
retval = -EINVAL;
goto out_put_task;
}
if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
retval = -ENOMEM;
goto out_put_task;
}
if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
retval = -ENOMEM;
goto out_free_cpus_allowed;
}
retval = -EPERM;
if (!check_same_owner(p)) {
rcu_read_lock();
if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
rcu_read_unlock();
goto out_free_new_mask;
}
rcu_read_unlock();
}
retval = security_task_setscheduler(p);
if (retval)
goto out_free_new_mask;
cpuset_cpus_allowed(p, cpus_allowed);
cpumask_and(new_mask, in_mask, cpus_allowed);
cpumask_and(new_mask, mask, cpus_allowed);
/*
* Since bandwidth control happens on root_domain basis,
@ -7661,23 +7630,63 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
#endif
again:
retval = __set_cpus_allowed_ptr(p, new_mask, SCA_CHECK);
if (retval)
goto out_free_new_mask;
if (!retval) {
cpuset_cpus_allowed(p, cpus_allowed);
if (!cpumask_subset(new_mask, cpus_allowed)) {
/*
* We must have raced with a concurrent cpuset
* update. Just reset the cpus_allowed to the
* cpuset's cpus_allowed
*/
cpumask_copy(new_mask, cpus_allowed);
goto again;
}
cpuset_cpus_allowed(p, cpus_allowed);
if (!cpumask_subset(new_mask, cpus_allowed)) {
/*
* We must have raced with a concurrent cpuset update.
* Just reset the cpumask to the cpuset's cpus_allowed.
*/
cpumask_copy(new_mask, cpus_allowed);
goto again;
}
out_free_new_mask:
free_cpumask_var(new_mask);
out_free_cpus_allowed:
free_cpumask_var(cpus_allowed);
return retval;
}
long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
{
struct task_struct *p;
int retval;
rcu_read_lock();
p = find_process_by_pid(pid);
if (!p) {
rcu_read_unlock();
return -ESRCH;
}
/* Prevent p going away */
get_task_struct(p);
rcu_read_unlock();
if (p->flags & PF_NO_SETAFFINITY) {
retval = -EINVAL;
goto out_put_task;
}
if (!check_same_owner(p)) {
rcu_read_lock();
if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
rcu_read_unlock();
retval = -EPERM;
goto out_put_task;
}
rcu_read_unlock();
}
retval = security_task_setscheduler(p);
if (retval)
goto out_put_task;
retval = __sched_setaffinity(p, in_mask);
out_put_task:
put_task_struct(p);
return retval;