Messages in this thread | | | Date | Wed, 19 Jan 2022 07:43:23 -0800 | From | Tadeusz Struk <> | Subject | Re: [PATCH] sched/fair: Fix fault in reweight_entity |
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On 1/19/22 01:32, Peter Zijlstra wrote: > On Tue, Jan 18, 2022 at 05:24:17PM -0800, Tadeusz Struk wrote: >> Syzbot found a GPF in reweight_entity. This has been bisected to commit >> c85c6fadbef0 ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") > That's a stable commit, the real commit is 4ef0c5c6b5ba1f38f0ea1cedad0cad722f00c14a
This is what syzbot bisected it to. I will reference the original commit in the next version.
> >> Looks like after this change there is a time window, when >> task_struct->se.cfs_rq can be NULL. This can be exploited to trigger >> null-ptr-deref by calling setpriority on that task. > Looks like isn't good enough, either there is, in which case you explain > the window, or there isn't in which case what are we doing here?
There surely is something wrong, otherwise it wouldn't crash. I will try to narrow down the reproducer to better understand what causes the fault.
-- Thanks, Tadeusz
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