Messages in this thread | | | Date | Fri, 19 Aug 2022 13:25:37 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH 5.10 1/1] sched/fair: Fix fault in reweight_entity |
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On Fri, Aug 19, 2022 at 10:11:40AM +0300, Fedor Pchelkin wrote: > From: Tadeusz Struk <tadeusz.struk@linaro.org> > > commit 13765de8148f71fa795e0a6607de37c49ea5915a upstream. > > Syzbot found a GPF in reweight_entity. This has been bisected to > commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid > sched_task_group") > > There is a race between sched_post_fork() and setpriority(PRIO_PGRP) > within a thread group that causes a null-ptr-deref in > reweight_entity() in CFS. The scenario is that the main process spawns > number of new threads, which then call setpriority(PRIO_PGRP, 0, -20), > wait, and exit. For each of the new threads the copy_process() gets > invoked, which adds the new task_struct and calls sched_post_fork() > for it. > > In the above scenario there is a possibility that > setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread > in the group that is just being created by copy_process(), and for > which the sched_post_fork() has not been executed yet. This will > trigger a null pointer dereference in reweight_entity(), as it will > try to access the run queue pointer, which hasn't been set. > > Before the mentioned change the cfs_rq pointer for the task has been > set in sched_fork(), which is called much earlier in copy_process(), > before the new task is added to the thread_group. Now it is done in > the sched_post_fork(), which is called after that. To fix the issue > the remove the update_load param from the update_load param() function > and call reweight_task() only if the task flag doesn't have the > TASK_NEW flag set. > > Fixes: 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") > Reported-by: syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com > Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> > Cc: stable@vger.kernel.org > Link: https://lkml.kernel.org/r/20220203161846.1160750-1-tadeusz.struk@linaro.org > Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru> > --- > 5.10 adaptation: Replaced a task_struct field '__state' with 'state'
Now queued up, thanks.
greg k-h
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