Messages in this thread | | | Subject | Re: [PATCH 17/19] sched: Inherit task cookie on fork() | From | Chris Hyser <> | Date | Mon, 10 May 2021 12:22:55 -0400 |
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On 5/10/21 12:06 PM, Joel Fernandes wrote: > Hi Peter, > > On Thu, Apr 22, 2021 at 8:36 AM Peter Zijlstra <peterz@infradead.org> wrote: >> >> Note that sched_core_fork() is called from under tasklist_lock, and >> not from sched_fork() earlier. This avoids a few races later. >> >> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> >> --- >> include/linux/sched.h | 2 ++ >> kernel/fork.c | 3 +++ >> kernel/sched/core_sched.c | 6 ++++++ >> 3 files changed, 11 insertions(+) >> >> --- a/include/linux/sched.h >> +++ b/include/linux/sched.h >> @@ -2172,8 +2172,10 @@ const struct cpumask *sched_trace_rd_spa >> >> #ifdef CONFIG_SCHED_CORE >> extern void sched_core_free(struct task_struct *tsk); >> +extern void sched_core_fork(struct task_struct *p); >> #else >> static inline void sched_core_free(struct task_struct *tsk) { } >> +static inline void sched_core_fork(struct task_struct *p) { } >> #endif >> >> #endif >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -2249,6 +2249,8 @@ static __latent_entropy struct task_stru >> >> klp_copy_process(p); >> >> + sched_core_fork(p); >> + >> spin_lock(¤t->sighand->siglock); >> >> /* >> @@ -2336,6 +2338,7 @@ static __latent_entropy struct task_stru >> return p; >> >> bad_fork_cancel_cgroup: >> + sched_core_free(p); >> spin_unlock(¤t->sighand->siglock); >> write_unlock_irq(&tasklist_lock); >> cgroup_cancel_fork(p, args); >> --- a/kernel/sched/core_sched.c >> +++ b/kernel/sched/core_sched.c >> @@ -100,6 +100,12 @@ static unsigned long sched_core_clone_co >> return cookie; >> } >> >> +void sched_core_fork(struct task_struct *p) >> +{ >> + RB_CLEAR_NODE(&p->core_node); >> + p->core_cookie = sched_core_clone_cookie(current); > > Does this make sense also for !CLONE_THREAD forks?
Yes. Given the absence of a cgroup interface, fork inheritance (clone the cookie) is the best way to create shared cookie hierarchies. The security issue you mentioned was handled in my original code by setting a unique cookie on 'exec', but Peter took that out for the reason mentioned above. It was part of the "lets get this in compromise" effort.
-chrish
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