From: Quentin Perret qperret@google.com
[ Upstream commit f95091536f78971b269ec321b057b8d630b0ad8a ]
It is possible for sched_getattr() to incorrectly report the state of the reset_on_fork flag when called on a deadline task.
Indeed, if the flag was set on a deadline task using sched_setattr() with flags (SCHED_FLAG_RESET_ON_FORK | SCHED_FLAG_KEEP_PARAMS), then p->sched_reset_on_fork will be set, but __setscheduler() will bail out early, which means that the dl_se->flags will not get updated by __setscheduler_params()->__setparam_dl(). Consequently, if sched_getattr() is then called on the task, __getparam_dl() will override kattr.sched_flags with the now out-of-date copy in dl_se->flags and report the stale value to userspace.
To fix this, make sure to only copy the flags that are relevant to sched_deadline to and from the dl_se->flags field.
Signed-off-by: Quentin Perret qperret@google.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lore.kernel.org/r/20210727101103.2729607-2-qperret@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/deadline.c | 7 ++++--- kernel/sched/sched.h | 2 ++ 2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index aa592dc3cb40..9b2bb5f3ce09 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2615,7 +2615,7 @@ void __setparam_dl(struct task_struct *p, const struct sched_attr *attr) dl_se->dl_runtime = attr->sched_runtime; dl_se->dl_deadline = attr->sched_deadline; dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline; - dl_se->flags = attr->sched_flags; + dl_se->flags = attr->sched_flags & SCHED_DL_FLAGS; dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime); dl_se->dl_density = to_ratio(dl_se->dl_deadline, dl_se->dl_runtime); } @@ -2628,7 +2628,8 @@ void __getparam_dl(struct task_struct *p, struct sched_attr *attr) attr->sched_runtime = dl_se->dl_runtime; attr->sched_deadline = dl_se->dl_deadline; attr->sched_period = dl_se->dl_period; - attr->sched_flags = dl_se->flags; + attr->sched_flags &= ~SCHED_DL_FLAGS; + attr->sched_flags |= dl_se->flags; }
/* @@ -2703,7 +2704,7 @@ bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr) if (dl_se->dl_runtime != attr->sched_runtime || dl_se->dl_deadline != attr->sched_deadline || dl_se->dl_period != attr->sched_period || - dl_se->flags != attr->sched_flags) + dl_se->flags != (attr->sched_flags & SCHED_DL_FLAGS)) return true;
return false; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 7b7ba91e319b..55e695080fc6 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -209,6 +209,8 @@ static inline int task_has_dl_policy(struct task_struct *p) */ #define SCHED_FLAG_SUGOV 0x10000000
+#define SCHED_DL_FLAGS (SCHED_FLAG_RECLAIM | SCHED_FLAG_DL_OVERRUN | SCHED_FLAG_SUGOV) + static inline bool dl_entity_is_special(struct sched_dl_entity *dl_se) { #ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL