On Mon, Jun 13, 2022 at 01:55:31PM +0000, Zhang, Qiang1 wrote:
> > syzbot <syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com> writes:
> >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: 6d0c80680317 Add linux-next specific files for 20220610
> > > git tree: linux-next
> > > console output:
> > > https://syzkaller.appspot.com/x/log.txt?x=13b52c2ff00000
> > > kernel config:
> > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641
> > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > I don't understand what is going on in linux-next kernel/rcu/tasks.h
> > looks different than in Linus's tree. Paul does that mean you have
> > some staged rcu changes?
>
> >Less than 100 RCU-related patches in -rcu, so not all that bad. ;-)
> >
> >But yes, this could possibly be an issue in one of those patches.
>
> > Eric
> >
> >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com
> > >
> > > ------------[ cut here ]------------
> > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > exit_tasks_rcu_finish_trace kernel/rcu/tasks.h:1664 [inline]
> > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > exit_tasks_rcu_finish+0x122/0x1b0 kernel/rcu/tasks.h:1006
>
> >The usual way for this warning to trigger is for these a task to exit while in an RCU Tasks Trace read-side critical section:
> >
> > rcu_read_lock_trace();
> > do_something_that_causes_task_exit();
> >
>
> Hi Paul, wether the following scenarios be considered
>
> rcu_read_unlock_trace_special
> ->if (trs.b.blocked)
> ->raw_spin_lock_irqsave_rcu_node
> ->list_del_init(&t->trc_blkd_node)
> ->WRITE_ONCE(t->trc_reader_special.b.blocked, false)
> ->raw_spin_unlock_irqrestore_rcu_node
> ->Inerrrupt
> ->schedule
> ->rcu_note_context_switch
> ->rcu_tasks_trace_qs
> If (___rttq_nesting && !READ_ONCE((t)->trc_reader_special.b.blocked)
> /*___rttq_nesting ==1 && (t)->trc_reader_special.b.blocked =false*/
> rcu_tasks_trace_qs_blkd(t)
> ->WRITE_ONCE(t->trc_reader_nesting, 0)
> .......
> -> exit_tasks_rcu_finish
>
> Whether the following patch can fix it, or what am I missing?
> Any thoughts?
>
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index
> f1209ce621c5..c607e4c914d3 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -1247,6 +1247,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> struct rcu_tasks_percpu *rtpcp;
> union rcu_special trs;
>
> + WRITE_ONCE(t->trc_reader_nesting, 0);
> // Open-coded full-word version of rcu_ld_need_qs().
> smp_mb(); // Enforce full grace-period ordering.
> trs = smp_load_acquire(&t->trc_reader_special);
> @@ -1267,7 +1268,6 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> WRITE_ONCE(t->trc_reader_special.b.blocked, false);
> raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
> }
> - WRITE_ONCE(t->trc_reader_nesting, 0);
> }
> EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special);
>Thank you for looking into this!
>
>You do have what I believe to be the correct failure scenario, but the above fix would break nested RCU Tasks Trace read-side critical sections.
Hi Paul
Break nested RCU Tasks Trace read-side critical sections?
Does it mean the following?
rcu_read_unlock_trace
-> WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
/* t->trc_reader_special.s == 0*/
-> if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting)
-> Interrupt
-> schedule
-> rcu_note_context_switch
-> rcu_tasks_trace_qs
/*___rttq_nesting == INT_MIN && (t)->trc_reader_special.b.blocked == false*/
->rcu_tasks_trace_qs_blkd(t)
/*nesting == 0*/
-> WRITE_ONCE(t->trc_reader_nesting, nesting);
-> return;
.........
exit_tasks_rcu_finish
trigger Warnings
Or where am I misunderstanding?
Thanks
Zqiang
>
>But would you be willing to try out the patch shown below?
I will try to test it.
>
> Thanx, Paul
>
>------------------------------------------------------------------------
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 08059d8d4f5a7..937a58b3266bf 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -184,7 +184,7 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
likely(!___rttq_nesting)) { \
rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
- } else if (___rttq_nesting && \
+ } else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
!READ_ONCE((t)->trc_reader_special.b.blocked)) { \
rcu_tasks_trace_qs_blkd(t); \
} \
diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h index 6f9c358173989..9bc8cbb33340b 100644
--- a/include/linux/rcupdate_trace.h
+++ b/include/linux/rcupdate_trace.h
@@ -75,7 +75,7 @@ static inline void rcu_read_unlock_trace(void)
nesting = READ_ONCE(t->trc_reader_nesting) - 1;
barrier(); // Critical section before disabling.
// Disable IPI-based setting of .need_qs.
- WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
+ WRITE_ONCE(t->trc_reader_nesting, INT_MIN + nesting);
if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) {
WRITE_ONCE(t->trc_reader_nesting, nesting);
return; // We assume shallow reader nesting.On Mon, Jun 13, 2022 at 10:26:47PM +0000, Zhang, Qiang1 wrote:
> On Mon, Jun 13, 2022 at 01:55:31PM +0000, Zhang, Qiang1 wrote:
> > > syzbot <syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com> writes:
> > >
> > > > Hello,
> > > >
> > > > syzbot found the following issue on:
> > > >
> > > > HEAD commit: 6d0c80680317 Add linux-next specific files for 20220610
> > > > git tree: linux-next
> > > > console output:
> > > > https://syzkaller.appspot.com/x/log.txt?x=13b52c2ff00000
> > > > kernel config:
> > > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641
> > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > >
> > > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > I don't understand what is going on in linux-next kernel/rcu/tasks.h
> > > looks different than in Linus's tree. Paul does that mean you have
> > > some staged rcu changes?
> >
> > >Less than 100 RCU-related patches in -rcu, so not all that bad. ;-)
> > >
> > >But yes, this could possibly be an issue in one of those patches.
> >
> > > Eric
> > >
> > >
> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > Reported-by: syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com
> > > >
> > > > ------------[ cut here ]------------
> > > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > > exit_tasks_rcu_finish_trace kernel/rcu/tasks.h:1664 [inline]
> > > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > > exit_tasks_rcu_finish+0x122/0x1b0 kernel/rcu/tasks.h:1006
> >
> > >The usual way for this warning to trigger is for these a task to exit while in an RCU Tasks Trace read-side critical section:
> > >
> > > rcu_read_lock_trace();
> > > do_something_that_causes_task_exit();
> > >
> >
> > Hi Paul, wether the following scenarios be considered
> >
> > rcu_read_unlock_trace_special
> > ->if (trs.b.blocked)
> > ->raw_spin_lock_irqsave_rcu_node
> > ->list_del_init(&t->trc_blkd_node)
> > ->WRITE_ONCE(t->trc_reader_special.b.blocked, false)
> > ->raw_spin_unlock_irqrestore_rcu_node
> > ->Inerrrupt
> > ->schedule
> > ->rcu_note_context_switch
> > ->rcu_tasks_trace_qs
> > If (___rttq_nesting && !READ_ONCE((t)->trc_reader_special.b.blocked)
> > /*___rttq_nesting ==1 && (t)->trc_reader_special.b.blocked =false*/
> > rcu_tasks_trace_qs_blkd(t)
> > ->WRITE_ONCE(t->trc_reader_nesting, 0)
> > .......
> > -> exit_tasks_rcu_finish
> >
> > Whether the following patch can fix it, or what am I missing?
> > Any thoughts?
> >
> > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index
> > f1209ce621c5..c607e4c914d3 100644
> > --- a/kernel/rcu/tasks.h
> > +++ b/kernel/rcu/tasks.h
> > @@ -1247,6 +1247,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> > struct rcu_tasks_percpu *rtpcp;
> > union rcu_special trs;
> >
> > + WRITE_ONCE(t->trc_reader_nesting, 0);
> > // Open-coded full-word version of rcu_ld_need_qs().
> > smp_mb(); // Enforce full grace-period ordering.
> > trs = smp_load_acquire(&t->trc_reader_special);
> > @@ -1267,7 +1268,6 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> > WRITE_ONCE(t->trc_reader_special.b.blocked, false);
> > raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
> > }
> > - WRITE_ONCE(t->trc_reader_nesting, 0);
> > }
> > EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special);
>
> >Thank you for looking into this!
> >
> >You do have what I believe to be the correct failure scenario, but the above fix would break nested RCU Tasks Trace read-side critical sections.
>
> Hi Paul
>
> Break nested RCU Tasks Trace read-side critical sections?
> Does it mean the following?
>
> rcu_read_unlock_trace
> -> WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
> /* t->trc_reader_special.s == 0*/
> -> if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting)
> -> Interrupt
> -> schedule
> -> rcu_note_context_switch
> -> rcu_tasks_trace_qs
> /*___rttq_nesting == INT_MIN && (t)->trc_reader_special.b.blocked == false*/
> ->rcu_tasks_trace_qs_blkd(t)
> /*nesting == 0*/
> -> WRITE_ONCE(t->trc_reader_nesting, nesting);
> -> return;
> .........
> exit_tasks_rcu_finish
> trigger Warnings
>
> Or where am I misunderstanding?
I suspect that you do in fact understand it. Let's walk through the
failure scenario again and see.
If that READ_ONCE(t->trc_reader_special.s) return zero as you suggest,
and then the interrupt and schedule happen as you suggest, then
rcu_tasks_trace_qs_blkd() will see a non-zero ->trc_reader_nesting and
a zero .b.blocked. It queues the task, but rcu_read_unlock_trace()
won't check again. It will set ->trc_reader_nesting to zero and
continue. As you noted, if the task exits in that state, then
exit_tasks_rcu_finish_trace() will trigger its WARN_ON_ONCE().
Your change won't affect this because rcu_read_unlock_trace_special()
never gets called.
Hence the approach in the patch below.
Do you see any failure modes given the below patch?
> Thanks
> Zqiang
>
> >
> >But would you be willing to try out the patch shown below?
>
> I will try to test it.
Thank you very much!
Thanx, Paul
> >------------------------------------------------------------------------
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 08059d8d4f5a7..937a58b3266bf 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -184,7 +184,7 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
> if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
> likely(!___rttq_nesting)) { \
> rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
> - } else if (___rttq_nesting && \
> + } else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
> !READ_ONCE((t)->trc_reader_special.b.blocked)) { \
> rcu_tasks_trace_qs_blkd(t); \
> } \
> diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h index 6f9c358173989..9bc8cbb33340b 100644
> --- a/include/linux/rcupdate_trace.h
> +++ b/include/linux/rcupdate_trace.h
> @@ -75,7 +75,7 @@ static inline void rcu_read_unlock_trace(void)
> nesting = READ_ONCE(t->trc_reader_nesting) - 1;
> barrier(); // Critical section before disabling.
> // Disable IPI-based setting of .need_qs.
> - WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
> + WRITE_ONCE(t->trc_reader_nesting, INT_MIN + nesting);
> if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) {
> WRITE_ONCE(t->trc_reader_nesting, nesting);
> return; // We assume shallow reader nesting.
On Mon, Jun 13, 2022 at 10:26:47PM +0000, Zhang, Qiang1 wrote:
> On Mon, Jun 13, 2022 at 01:55:31PM +0000, Zhang, Qiang1 wrote:
> > > syzbot <syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com> writes:
> > >
> > > > Hello,
> > > >
> > > > syzbot found the following issue on:
> > > >
> > > > HEAD commit: 6d0c80680317 Add linux-next specific files for 20220610
> > > > git tree: linux-next
> > > > console output:
> > > > https://syzkaller.appspot.com/x/log.txt?x=13b52c2ff00000
> > > > kernel config:
> > > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641
> > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > >
> > > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > I don't understand what is going on in linux-next
> > > kernel/rcu/tasks.h looks different than in Linus's tree. Paul
> > > does that mean you have some staged rcu changes?
> >
> > >Less than 100 RCU-related patches in -rcu, so not all that bad.
> > >;-)
> > >
> > >But yes, this could possibly be an issue in one of those patches.
> >
> > > Eric
> > >
> > >
> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > Reported-by:
> > > > syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com
> > > >
> > > > ------------[ cut here ]------------
> > > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > > exit_tasks_rcu_finish_trace kernel/rcu/tasks.h:1664 [inline]
> > > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > > exit_tasks_rcu_finish+0x122/0x1b0 kernel/rcu/tasks.h:1006
> >
> > >The usual way for this warning to trigger is for these a task to exit while in an RCU Tasks Trace read-side critical section:
> > >
> > > rcu_read_lock_trace();
> > > do_something_that_causes_task_exit();
> > >
> >
> > Hi Paul, wether the following scenarios be considered
> >
> > rcu_read_unlock_trace_special
> > ->if (trs.b.blocked)
> > ->raw_spin_lock_irqsave_rcu_node
> > ->list_del_init(&t->trc_blkd_node)
> > ->WRITE_ONCE(t->trc_reader_special.b.blocked, false)
> > ->raw_spin_unlock_irqrestore_rcu_node
> > ->Inerrrupt
> > ->schedule
> > ->rcu_note_context_switch
> > ->rcu_tasks_trace_qs
> > If (___rttq_nesting && !READ_ONCE((t)->trc_reader_special.b.blocked)
> > /*___rttq_nesting ==1 && (t)->trc_reader_special.b.blocked =false*/
> > rcu_tasks_trace_qs_blkd(t)
> > ->WRITE_ONCE(t->trc_reader_nesting, 0)
> > .......
> > -> exit_tasks_rcu_finish
> >
> > Whether the following patch can fix it, or what am I missing?
> > Any thoughts?
> >
> > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index
> > f1209ce621c5..c607e4c914d3 100644
> > --- a/kernel/rcu/tasks.h
> > +++ b/kernel/rcu/tasks.h
> > @@ -1247,6 +1247,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> > struct rcu_tasks_percpu *rtpcp;
> > union rcu_special trs;
> >
> > + WRITE_ONCE(t->trc_reader_nesting, 0);
> > // Open-coded full-word version of rcu_ld_need_qs().
> > smp_mb(); // Enforce full grace-period ordering.
> > trs = smp_load_acquire(&t->trc_reader_special);
> > @@ -1267,7 +1268,6 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> > WRITE_ONCE(t->trc_reader_special.b.blocked, false);
> > raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
> > }
> > - WRITE_ONCE(t->trc_reader_nesting, 0);
> > }
> > EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special);
>
> >Thank you for looking into this!
> >
> >You do have what I believe to be the correct failure scenario, but the above fix would break nested RCU Tasks Trace read-side critical sections.
>
> Hi Paul
>
> Break nested RCU Tasks Trace read-side critical sections?
> Does it mean the following?
>
> rcu_read_unlock_trace
> -> WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
> /* t->trc_reader_special.s == 0*/
> -> if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting)
> -> Interrupt
> -> schedule
> -> rcu_note_context_switch
> -> rcu_tasks_trace_qs
> /*___rttq_nesting == INT_MIN && (t)->trc_reader_special.b.blocked == false*/
> ->rcu_tasks_trace_qs_blkd(t)
> /*nesting == 0*/
> -> WRITE_ONCE(t->trc_reader_nesting, nesting);
> -> return;
> .........
> exit_tasks_rcu_finish
> trigger Warnings
>
> Or where am I misunderstanding?
>I suspect that you do in fact understand it. Let's walk through the failure scenario again and see.
>
>If that READ_ONCE(t->trc_reader_special.s) return zero as you suggest, and then the interrupt and schedule happen as you suggest, then
>rcu_tasks_trace_qs_blkd() will see a non-zero ->trc_reader_nesting and a zero .b.blocked. It queues the task, but rcu_read_unlock_trace() won't check again. It will set ->trc_reader_nesting to zero and continue. As you noted, if the task exits in that state, then
>exit_tasks_rcu_finish_trace() will trigger its WARN_ON_ONCE().
I understand the problem you describe, Just like the call flow I described above,
rcu_read_unlock_trace_special() may not be called.
Thanks
Zqiang
>
>Your change won't affect this because rcu_read_unlock_trace_special() never gets called.
>
>Hence the approach in the patch below.
>
>Do you see any failure modes given the below patch?
> Thanks
> Zqiang
>
> >
> >But would you be willing to try out the patch shown below?
>
> I will try to test it.
>Thank you very much!
>
> Thanx, Paul
> >---------------------------------------------------------------------
> >---
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index
> 08059d8d4f5a7..937a58b3266bf 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -184,7 +184,7 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
> if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
> likely(!___rttq_nesting)) { \
> rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
> - } else if (___rttq_nesting && \
> + } else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
> !READ_ONCE((t)->trc_reader_special.b.blocked)) { \
> rcu_tasks_trace_qs_blkd(t); \
> } \
> diff --git a/include/linux/rcupdate_trace.h
> b/include/linux/rcupdate_trace.h index 6f9c358173989..9bc8cbb33340b
> 100644
> --- a/include/linux/rcupdate_trace.h
> +++ b/include/linux/rcupdate_trace.h
> @@ -75,7 +75,7 @@ static inline void rcu_read_unlock_trace(void)
> nesting = READ_ONCE(t->trc_reader_nesting) - 1;
> barrier(); // Critical section before disabling.
> // Disable IPI-based setting of .need_qs.
> - WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
> + WRITE_ONCE(t->trc_reader_nesting, INT_MIN + nesting);
> if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) {
> WRITE_ONCE(t->trc_reader_nesting, nesting);
> return; // We assume shallow reader nesting.
On Mon, Jun 13, 2022 at 11:54:45PM +0000, Zhang, Qiang1 wrote:
> On Mon, Jun 13, 2022 at 10:26:47PM +0000, Zhang, Qiang1 wrote:
> > On Mon, Jun 13, 2022 at 01:55:31PM +0000, Zhang, Qiang1 wrote:
> > > > syzbot <syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com> writes:
> > > >
> > > > > Hello,
> > > > >
> > > > > syzbot found the following issue on:
> > > > >
> > > > > HEAD commit: 6d0c80680317 Add linux-next specific files for 20220610
> > > > > git tree: linux-next
> > > > > console output:
> > > > > https://syzkaller.appspot.com/x/log.txt?x=13b52c2ff00000
> > > > > kernel config:
> > > > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
> > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641
> > > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > > >
> > > > > Unfortunately, I don't have any reproducer for this issue yet.
> > > >
> > > > I don't understand what is going on in linux-next
> > > > kernel/rcu/tasks.h looks different than in Linus's tree. Paul
> > > > does that mean you have some staged rcu changes?
> > >
> > > >Less than 100 RCU-related patches in -rcu, so not all that bad.
> > > >;-)
> > > >
> > > >But yes, this could possibly be an issue in one of those patches.
> > >
> > > > Eric
> > > >
> > > >
> > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > > Reported-by:
> > > > > syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com
> > > > >
> > > > > ------------[ cut here ]------------
> > > > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > > > exit_tasks_rcu_finish_trace kernel/rcu/tasks.h:1664 [inline]
> > > > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > > > exit_tasks_rcu_finish+0x122/0x1b0 kernel/rcu/tasks.h:1006
> > >
> > > >The usual way for this warning to trigger is for these a task to exit while in an RCU Tasks Trace read-side critical section:
> > > >
> > > > rcu_read_lock_trace();
> > > > do_something_that_causes_task_exit();
> > > >
> > >
> > > Hi Paul, wether the following scenarios be considered
> > >
> > > rcu_read_unlock_trace_special
> > > ->if (trs.b.blocked)
> > > ->raw_spin_lock_irqsave_rcu_node
> > > ->list_del_init(&t->trc_blkd_node)
> > > ->WRITE_ONCE(t->trc_reader_special.b.blocked, false)
> > > ->raw_spin_unlock_irqrestore_rcu_node
> > > ->Inerrrupt
> > > ->schedule
> > > ->rcu_note_context_switch
> > > ->rcu_tasks_trace_qs
> > > If (___rttq_nesting && !READ_ONCE((t)->trc_reader_special.b.blocked)
> > > /*___rttq_nesting ==1 && (t)->trc_reader_special.b.blocked =false*/
> > > rcu_tasks_trace_qs_blkd(t)
> > > ->WRITE_ONCE(t->trc_reader_nesting, 0)
> > > .......
> > > -> exit_tasks_rcu_finish
> > >
> > > Whether the following patch can fix it, or what am I missing?
> > > Any thoughts?
> > >
> > > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index
> > > f1209ce621c5..c607e4c914d3 100644
> > > --- a/kernel/rcu/tasks.h
> > > +++ b/kernel/rcu/tasks.h
> > > @@ -1247,6 +1247,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> > > struct rcu_tasks_percpu *rtpcp;
> > > union rcu_special trs;
> > >
> > > + WRITE_ONCE(t->trc_reader_nesting, 0);
> > > // Open-coded full-word version of rcu_ld_need_qs().
> > > smp_mb(); // Enforce full grace-period ordering.
> > > trs = smp_load_acquire(&t->trc_reader_special);
> > > @@ -1267,7 +1268,6 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> > > WRITE_ONCE(t->trc_reader_special.b.blocked, false);
> > > raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
> > > }
> > > - WRITE_ONCE(t->trc_reader_nesting, 0);
> > > }
> > > EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special);
> >
> > >Thank you for looking into this!
> > >
> > >You do have what I believe to be the correct failure scenario, but the above fix would break nested RCU Tasks Trace read-side critical sections.
> >
> > Hi Paul
> >
> > Break nested RCU Tasks Trace read-side critical sections?
> > Does it mean the following?
> >
> > rcu_read_unlock_trace
> > -> WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
> > /* t->trc_reader_special.s == 0*/
> > -> if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting)
> > -> Interrupt
> > -> schedule
> > -> rcu_note_context_switch
> > -> rcu_tasks_trace_qs
> > /*___rttq_nesting == INT_MIN && (t)->trc_reader_special.b.blocked == false*/
> > ->rcu_tasks_trace_qs_blkd(t)
> > /*nesting == 0*/
> > -> WRITE_ONCE(t->trc_reader_nesting, nesting);
> > -> return;
> > .........
> > exit_tasks_rcu_finish
> > trigger Warnings
> >
> > Or where am I misunderstanding?
>
> >I suspect that you do in fact understand it. Let's walk through the failure scenario again and see.
> >
> >If that READ_ONCE(t->trc_reader_special.s) return zero as you suggest, and then the interrupt and schedule happen as you suggest, then
> >rcu_tasks_trace_qs_blkd() will see a non-zero ->trc_reader_nesting and a zero .b.blocked. It queues the task, but rcu_read_unlock_trace() won't check again. It will set ->trc_reader_nesting to zero and continue. As you noted, if the task exits in that state, then
> >exit_tasks_rcu_finish_trace() will trigger its WARN_ON_ONCE().
>
> I understand the problem you describe, Just like the call flow I described above,
> rcu_read_unlock_trace_special() may not be called.
Very good!
Thanx, Paul
> Thanks
> Zqiang
>
> >
> >Your change won't affect this because rcu_read_unlock_trace_special() never gets called.
> >
> >Hence the approach in the patch below.
> >
> >Do you see any failure modes given the below patch?
>
> > Thanks
> > Zqiang
> >
> > >
> > >But would you be willing to try out the patch shown below?
> >
> > I will try to test it.
>
> >Thank you very much!
> >
> > Thanx, Paul
>
> > >---------------------------------------------------------------------
> > >---
> >
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index
> > 08059d8d4f5a7..937a58b3266bf 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -184,7 +184,7 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
> > if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
> > likely(!___rttq_nesting)) { \
> > rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
> > - } else if (___rttq_nesting && \
> > + } else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
> > !READ_ONCE((t)->trc_reader_special.b.blocked)) { \
> > rcu_tasks_trace_qs_blkd(t); \
> > } \
> > diff --git a/include/linux/rcupdate_trace.h
> > b/include/linux/rcupdate_trace.h index 6f9c358173989..9bc8cbb33340b
> > 100644
> > --- a/include/linux/rcupdate_trace.h
> > +++ b/include/linux/rcupdate_trace.h
> > @@ -75,7 +75,7 @@ static inline void rcu_read_unlock_trace(void)
> > nesting = READ_ONCE(t->trc_reader_nesting) - 1;
> > barrier(); // Critical section before disabling.
> > // Disable IPI-based setting of .need_qs.
> > - WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
> > + WRITE_ONCE(t->trc_reader_nesting, INT_MIN + nesting);
> > if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) {
> > WRITE_ONCE(t->trc_reader_nesting, nesting);
> > return; // We assume shallow reader nesting.
On Mon, Jun 13, 2022 at 10:26:47PM +0000, Zhang, Qiang1 wrote:
> On Mon, Jun 13, 2022 at 01:55:31PM +0000, Zhang, Qiang1 wrote:
> > > syzbot <syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com> writes:
> > >
> > > > Hello,
> > > >
> > > > syzbot found the following issue on:
> > > >
> > > > HEAD commit: 6d0c80680317 Add linux-next specific files for 20220610
> > > > git tree: linux-next
> > > > console output:
> > > > https://syzkaller.appspot.com/x/log.txt?x=13b52c2ff00000
> > > > kernel config:
> > > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641
> > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > >
> > > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > I don't understand what is going on in linux-next
> > > kernel/rcu/tasks.h looks different than in Linus's tree. Paul
> > > does that mean you have some staged rcu changes?
> >
> > >Less than 100 RCU-related patches in -rcu, so not all that bad.
> > >;-)
> > >
> > >But yes, this could possibly be an issue in one of those patches.
> >
> > > Eric
> > >
> > >
> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > Reported-by:
> > > > syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com
> > > >
> > > > ------------[ cut here ]------------
> > > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > > exit_tasks_rcu_finish_trace kernel/rcu/tasks.h:1664 [inline]
> > > > WARNING: CPU: 1 PID: 28639 at kernel/rcu/tasks.h:1664
> > > > exit_tasks_rcu_finish+0x122/0x1b0 kernel/rcu/tasks.h:1006
> >
> > >The usual way for this warning to trigger is for these a task to exit while in an RCU Tasks Trace read-side critical section:
> > >
> > > rcu_read_lock_trace();
> > > do_something_that_causes_task_exit();
> > >
> >
> > Hi Paul, wether the following scenarios be considered
> >
> > rcu_read_unlock_trace_special
> > ->if (trs.b.blocked)
> > ->raw_spin_lock_irqsave_rcu_node
> > ->list_del_init(&t->trc_blkd_node)
> > ->WRITE_ONCE(t->trc_reader_special.b.blocked, false)
> > ->raw_spin_unlock_irqrestore_rcu_node
> > ->Inerrrupt
> > ->schedule
> > ->rcu_note_context_switch
> > ->rcu_tasks_trace_qs
> > If (___rttq_nesting && !READ_ONCE((t)->trc_reader_special.b.blocked)
> > /*___rttq_nesting ==1 && (t)->trc_reader_special.b.blocked =false*/
> > rcu_tasks_trace_qs_blkd(t)
> > ->WRITE_ONCE(t->trc_reader_nesting, 0)
> > .......
> > -> exit_tasks_rcu_finish
> >
> > Whether the following patch can fix it, or what am I missing?
> > Any thoughts?
> >
> > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index
> > f1209ce621c5..c607e4c914d3 100644
> > --- a/kernel/rcu/tasks.h
> > +++ b/kernel/rcu/tasks.h
> > @@ -1247,6 +1247,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> > struct rcu_tasks_percpu *rtpcp;
> > union rcu_special trs;
> >
> > + WRITE_ONCE(t->trc_reader_nesting, 0);
> > // Open-coded full-word version of rcu_ld_need_qs().
> > smp_mb(); // Enforce full grace-period ordering.
> > trs = smp_load_acquire(&t->trc_reader_special);
> > @@ -1267,7 +1268,6 @@ void rcu_read_unlock_trace_special(struct task_struct *t)
> > WRITE_ONCE(t->trc_reader_special.b.blocked, false);
> > raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
> > }
> > - WRITE_ONCE(t->trc_reader_nesting, 0);
> > }
> > EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special);
>
> >Thank you for looking into this!
> >
> >You do have what I believe to be the correct failure scenario, but the above fix would break nested RCU Tasks Trace read-side critical sections.
>
> Hi Paul
>
> Break nested RCU Tasks Trace read-side critical sections?
> Does it mean the following?
>
> rcu_read_unlock_trace
> -> WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
> /* t->trc_reader_special.s == 0*/
> -> if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting)
> -> Interrupt
> -> schedule
> -> rcu_note_context_switch
> -> rcu_tasks_trace_qs
> /*___rttq_nesting == INT_MIN && (t)->trc_reader_special.b.blocked == false*/
> ->rcu_tasks_trace_qs_blkd(t)
> /*nesting == 0*/
> -> WRITE_ONCE(t->trc_reader_nesting, nesting);
> -> return;
Directly return.
> .........
> exit_tasks_rcu_finish
> trigger Warnings
>
My change ignores this, so I described the above scenario, the rcu_read_unlock_trace_special() is not be called.
Thanks
Zqiang
> Or where am I misunderstanding?
>I suspect that you do in fact understand it. Let's walk through the failure scenario again and see.
>
>If that READ_ONCE(t->trc_reader_special.s) return zero as you suggest,
>and then the interrupt and schedule happen as you suggest, then
>rcu_tasks_trace_qs_blkd() will see a non-zero ->trc_reader_nesting and
>a zero .b.blocked. It queues the task, but rcu_read_unlock_trace()
>won't check again. It will set ->trc_reader_nesting to zero and
>continue. As you noted, if the task exits in that state, then
>exit_tasks_rcu_finish_trace() will trigger its WARN_ON_ONCE().
I understand the problem you describe, Just like the call flow I described above,
rcu_read_unlock_trace_special() may not be called.
Thanks
Zqiang
>
>Your change won't affect this because rcu_read_unlock_trace_special() never gets called.
>
>Hence the approach in the patch below.
>
>Do you see any failure modes given the below patch?
> Thanks
> Zqiang
>
> >
> >But would you be willing to try out the patch shown below?
>
> I will try to test it.
>Thank you very much!
>
> Thanx, Paul
> >---------------------------------------------------------------------
> >---
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index
> 08059d8d4f5a7..937a58b3266bf 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -184,7 +184,7 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
> if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
> likely(!___rttq_nesting)) { \
> rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
> - } else if (___rttq_nesting && \
> + } else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
> !READ_ONCE((t)->trc_reader_special.b.blocked)) { \
> rcu_tasks_trace_qs_blkd(t); \
> } \
> diff --git a/include/linux/rcupdate_trace.h
> b/include/linux/rcupdate_trace.h index 6f9c358173989..9bc8cbb33340b
> 100644
> --- a/include/linux/rcupdate_trace.h
> +++ b/include/linux/rcupdate_trace.h
> @@ -75,7 +75,7 @@ static inline void rcu_read_unlock_trace(void)
> nesting = READ_ONCE(t->trc_reader_nesting) - 1;
> barrier(); // Critical section before disabling.
> // Disable IPI-based setting of .need_qs.
> - WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
> + WRITE_ONCE(t->trc_reader_nesting, INT_MIN + nesting);
> if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) {
> WRITE_ONCE(t->trc_reader_nesting, nesting);
> return; // We assume shallow reader nesting.
On Mon, Jun 13, 2022 at 10:36:07AM -0700, syzbot wrote: > Hello, > > syzbot has tested the proposed patch and the reproducer did not trigger any issue: > > Reported-and-tested-by: syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com Looks like the patch solved the reproducer. :) > Tested on: > > commit: 6d0c8068 Add linux-next specific files for 20220610 > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20220610 > console output: https://syzkaller.appspot.com/x/log.txt?x=12d068eff00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931 > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641 > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > patch: https://syzkaller.appspot.com/x/patch.diff?x=147f47c8080000 > > Note: testing is done by a robot and is best-effort only. You can see the dashboard link above for testing details... -- Kees Cook
On Mon, Jun 13, 2022 at 04:42:07PM -0700, Kees Cook wrote: > On Mon, Jun 13, 2022 at 10:36:07AM -0700, syzbot wrote: > > Hello, > > > > syzbot has tested the proposed patch and the reproducer did not trigger any issue: > > > > Reported-and-tested-by: syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com > > Looks like the patch solved the reproducer. :) For one of the two possible ways to make the bug happen. ;-) Still, good on Qiang for identifying one of the paths! Not just anyone can do that. Thanx, Paul > > Tested on: > > > > commit: 6d0c8068 Add linux-next specific files for 20220610 > > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20220610 > > console output: https://syzkaller.appspot.com/x/log.txt?x=12d068eff00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931 > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641 > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > patch: https://syzkaller.appspot.com/x/patch.diff?x=147f47c8080000 > > > > Note: testing is done by a robot and is best-effort only. > > You can see the dashboard link above for testing details... > > -- > Kees Cook
On Mon, Jun 13, 2022 at 04:42:07PM -0700, Kees Cook wrote: > On Mon, Jun 13, 2022 at 10:36:07AM -0700, syzbot wrote: > > Hello, > > > > syzbot has tested the proposed patch and the reproducer did not trigger any issue: > > > > Reported-and-tested-by: > > syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com > > Looks like the patch solved the reproducer. :) >For one of the two possible ways to make the bug happen. ;-) > >Still, good on Qiang for identifying one of the paths! Not just anyone can do that. Thanks Paul, yes this patch can solved the reproducer and I also test it. I compiled "bpf_test" according to the c file in the following link C reproducer: https://syzkaller.appspot.com/x/repro.c?x=148207bff00000 Not apply this patch, this calltrace reproduce root@qemux86-64:/# ./bpf_test ^C root@qemux86-64:/# dmesg [ 147.017232] ------------[ cut here ]------------ [ 147.017234] WARNING: CPU: 3 PID: 21586 at kernel/rcu/tasks.h:1664 exit_tasks_rcu_finish+0xbf/0x100 [ 147.017245] Modules linked in: [ 147.017249] CPU: 3 PID: 21586 Comm: bpf_test Not tainted 5.19.0-rc1-next-20220610-yoctodev-standard #204 [ 147.017253] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 [ 147.017256] RIP: 0010:exit_tasks_rcu_finish+0xbf/0x100 [ 147.017261] Code: 03 00 00 85 c0 75 59 f0 83 44 24 fc 00 49 8d bc 24 41 03 00 00 e8 21 09 2b 00 41 0f b6 84 24 41 03 00 00 83 e0 01 08 d8 74 11 <0f> 8 [ 147.017264] RSP: 0018:ffff88810ccd7af0 EFLAGS: 00010202 [ 147.017268] RAX: 0000000000000001 RBX: 0000000000000201 RCX: ffffffff897ab52f [ 147.017271] RDX: 1ffff1102181d7c8 RSI: 0000000000000000 RDI: ffff88810c0ebe41 [ 147.017274] RBP: ffff88810ccd7b08 R08: ffffffff897ab510 R09: 0000000000000000 [ 147.017277] R10: ffffffff8c407bbf R11: 0000000000000000 R12: ffff88810c0ebb00 [ 147.017279] R13: ffff88810c0ebe38 R14: ffff88810ccd7b78 R15: ffff88810ccd76b0 [ 147.017282] FS: 0000000000000000(0000) GS:ffff88815a000000(0000) knlGS:0000000000000000 [ 147.017287] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 147.017289] CR2: 0000000000000000 CR3: 000000011ac16000 CR4: 00000000001506e0 [ 147.017292] Call Trace: [ 147.017294] <TASK> [ 147.017297] do_exit+0xe9a/0x13a0 [ 147.017305] ? mm_update_next_owner+0x450/0x450 [ 147.017309] ? lock_downgrade+0x410/0x410 [ 147.017313] ? lock_contended+0x790/0x790 [ 147.017317] ? rcu_read_lock_held_common+0x1e/0x60 [ 147.017324] do_group_exit+0x71/0x150 [ 147.017329] get_signal+0x1319/0x1340 [ 147.017334] ? futex_wait_setup+0x180/0x180 [ 147.017341] ? exit_signals+0x4c0/0x4c0 [ 147.017345] ? futex_wake+0x29e/0x2e0 [ 147.017351] arch_do_signal_or_restart+0x9c/0xc60 [ 147.017357] ? rcu_read_lock_sched_held+0x60/0xd0 [ 147.017361] ? rcu_read_lock_bh_held+0xb0/0xb0 [ 147.017367] ? get_sigframe_size+0x20/0x20 [ 147.017371] ? do_futex+0x1a2/0x240 [ 147.017375] ? __ia32_sys_get_robust_list+0x240/0x240 [ 147.017378] ? __context_tracking_exit+0x91/0xa0 [ 147.017385] ? lock_downgrade+0x410/0x410 [ 147.017390] ? __x64_sys_futex+0x125/0x2b0 [ 147.017393] ? rcu_read_lock_held_common+0x1e/0x60 [ 147.017399] ? lockdep_hardirqs_on_prepare+0x13/0x230 [ 147.017403] ? exit_to_user_mode_prepare+0x151/0x240 [ 147.017409] exit_to_user_mode_prepare+0x16c/0x240 [ 147.017415] syscall_exit_to_user_mode+0x1e/0x70 [ 147.017419] do_syscall_64+0x50/0x90 [ 147.017423] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 147.017427] RIP: 0033:0x7f780e668fbd [ 147.017431] Code: Unable to access opcode bytes at RIP 0x7f780e668f93. [ 147.017433] RSP: 002b:00007f780e55bd48 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca [ 147.017437] RAX: fffffffffffffe00 RBX: 00007f780e55c640 RCX: 00007f780e668fbd [ 147.017440] RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000055ed9f3a8088 [ 147.017442] RBP: 00007f780e55bd60 R08: 0000000100000001 R09: 0000000100000001 [ 147.017445] R10: 0000000000000000 R11: 0000000000000246 R12: fffffffffffffeb0 [ 147.017447] R13: 0000000000000000 R14: 00007ffe5dcf20a0 R15: 00007f780e53c000 [ 147.017455] </TASK> [ 147.017458] irq event stamp: 0 [ 147.017460] hardirqs last enabled at (0): [<0000000000000000>] 0x0 [ 147.017463] hardirqs last disabled at (0): [<ffffffff896b5990>] copy_process+0xe30/0x35f0 [ 147.017467] softirqs last enabled at (0): [<ffffffff896b5990>] copy_process+0xe30/0x35f0 [ 147.017470] softirqs last disabled at (0): [<0000000000000000>] 0x0 [ 147.017473] ---[ end trace 0000000000000000 ]--- Apply this patch , this problem not reproduce. Thanks Zqiang > > Thanx, Paul > > > Tested on: > > > > commit: 6d0c8068 Add linux-next specific files for 20220610 > > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20220610 > > console output: > > https://syzkaller.appspot.com/x/log.txt?x=12d068eff00000 > > kernel config: > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931 > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641 > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > patch: https://syzkaller.appspot.com/x/patch.diff?x=147f47c8080000 > > > > Note: testing is done by a robot and is best-effort only. > > You can see the dashboard link above for testing details... > > -- > Kees Cook
On Tue, Jun 14, 2022 at 12:52:23AM +0000, Zhang, Qiang1 wrote: > On Mon, Jun 13, 2022 at 04:42:07PM -0700, Kees Cook wrote: > > On Mon, Jun 13, 2022 at 10:36:07AM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot has tested the proposed patch and the reproducer did not trigger any issue: > > > > > > Reported-and-tested-by: > > > syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com > > > > Looks like the patch solved the reproducer. :) > > >For one of the two possible ways to make the bug happen. ;-) > > > >Still, good on Qiang for identifying one of the paths! Not just anyone can do that. > > Thanks Paul, yes this patch can solved the reproducer and I also test it. > > I compiled "bpf_test" according to the c file in the following link > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=148207bff00000 > > Not apply this patch, this calltrace reproduce > > root@qemux86-64:/# ./bpf_test > ^C > root@qemux86-64:/# dmesg > [ 147.017232] ------------[ cut here ]------------ > [ 147.017234] WARNING: CPU: 3 PID: 21586 at kernel/rcu/tasks.h:1664 exit_tasks_rcu_finish+0xbf/0x100 > [ 147.017245] Modules linked in: > [ 147.017249] CPU: 3 PID: 21586 Comm: bpf_test Not tainted 5.19.0-rc1-next-20220610-yoctodev-standard #204 > [ 147.017253] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 > [ 147.017256] RIP: 0010:exit_tasks_rcu_finish+0xbf/0x100 > [ 147.017261] Code: 03 00 00 85 c0 75 59 f0 83 44 24 fc 00 49 8d bc 24 41 03 00 00 e8 21 09 2b 00 41 0f b6 84 24 41 03 00 00 83 e0 01 08 d8 74 11 <0f> 8 > [ 147.017264] RSP: 0018:ffff88810ccd7af0 EFLAGS: 00010202 > [ 147.017268] RAX: 0000000000000001 RBX: 0000000000000201 RCX: ffffffff897ab52f > [ 147.017271] RDX: 1ffff1102181d7c8 RSI: 0000000000000000 RDI: ffff88810c0ebe41 > [ 147.017274] RBP: ffff88810ccd7b08 R08: ffffffff897ab510 R09: 0000000000000000 > [ 147.017277] R10: ffffffff8c407bbf R11: 0000000000000000 R12: ffff88810c0ebb00 > [ 147.017279] R13: ffff88810c0ebe38 R14: ffff88810ccd7b78 R15: ffff88810ccd76b0 > [ 147.017282] FS: 0000000000000000(0000) GS:ffff88815a000000(0000) knlGS:0000000000000000 > [ 147.017287] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 147.017289] CR2: 0000000000000000 CR3: 000000011ac16000 CR4: 00000000001506e0 > [ 147.017292] Call Trace: > [ 147.017294] <TASK> > [ 147.017297] do_exit+0xe9a/0x13a0 > [ 147.017305] ? mm_update_next_owner+0x450/0x450 > [ 147.017309] ? lock_downgrade+0x410/0x410 > [ 147.017313] ? lock_contended+0x790/0x790 > [ 147.017317] ? rcu_read_lock_held_common+0x1e/0x60 > [ 147.017324] do_group_exit+0x71/0x150 > [ 147.017329] get_signal+0x1319/0x1340 > [ 147.017334] ? futex_wait_setup+0x180/0x180 > [ 147.017341] ? exit_signals+0x4c0/0x4c0 > [ 147.017345] ? futex_wake+0x29e/0x2e0 > [ 147.017351] arch_do_signal_or_restart+0x9c/0xc60 > [ 147.017357] ? rcu_read_lock_sched_held+0x60/0xd0 > [ 147.017361] ? rcu_read_lock_bh_held+0xb0/0xb0 > [ 147.017367] ? get_sigframe_size+0x20/0x20 > [ 147.017371] ? do_futex+0x1a2/0x240 > [ 147.017375] ? __ia32_sys_get_robust_list+0x240/0x240 > [ 147.017378] ? __context_tracking_exit+0x91/0xa0 > [ 147.017385] ? lock_downgrade+0x410/0x410 > [ 147.017390] ? __x64_sys_futex+0x125/0x2b0 > [ 147.017393] ? rcu_read_lock_held_common+0x1e/0x60 > [ 147.017399] ? lockdep_hardirqs_on_prepare+0x13/0x230 > [ 147.017403] ? exit_to_user_mode_prepare+0x151/0x240 > [ 147.017409] exit_to_user_mode_prepare+0x16c/0x240 > [ 147.017415] syscall_exit_to_user_mode+0x1e/0x70 > [ 147.017419] do_syscall_64+0x50/0x90 > [ 147.017423] entry_SYSCALL_64_after_hwframe+0x46/0xb0 > [ 147.017427] RIP: 0033:0x7f780e668fbd > [ 147.017431] Code: Unable to access opcode bytes at RIP 0x7f780e668f93. > [ 147.017433] RSP: 002b:00007f780e55bd48 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca > [ 147.017437] RAX: fffffffffffffe00 RBX: 00007f780e55c640 RCX: 00007f780e668fbd > [ 147.017440] RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000055ed9f3a8088 > [ 147.017442] RBP: 00007f780e55bd60 R08: 0000000100000001 R09: 0000000100000001 > [ 147.017445] R10: 0000000000000000 R11: 0000000000000246 R12: fffffffffffffeb0 > [ 147.017447] R13: 0000000000000000 R14: 00007ffe5dcf20a0 R15: 00007f780e53c000 > [ 147.017455] </TASK> > [ 147.017458] irq event stamp: 0 > [ 147.017460] hardirqs last enabled at (0): [<0000000000000000>] 0x0 > [ 147.017463] hardirqs last disabled at (0): [<ffffffff896b5990>] copy_process+0xe30/0x35f0 > [ 147.017467] softirqs last enabled at (0): [<ffffffff896b5990>] copy_process+0xe30/0x35f0 > [ 147.017470] softirqs last disabled at (0): [<0000000000000000>] 0x0 > [ 147.017473] ---[ end trace 0000000000000000 ]--- > > Apply this patch , this problem not reproduce. Thank you very much! May I apply your Tested-by? Thanx, Paul > Thanks > Zqiang > > > > > Thanx, Paul > > > > > Tested on: > > > > > > commit: 6d0c8068 Add linux-next specific files for 20220610 > > > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20220610 > > > console output: > > > https://syzkaller.appspot.com/x/log.txt?x=12d068eff00000 > > > kernel config: > > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641 > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > patch: https://syzkaller.appspot.com/x/patch.diff?x=147f47c8080000 > > > > > > Note: testing is done by a robot and is best-effort only. > > > > You can see the dashboard link above for testing details... > > > > -- > > Kees Cook
On Tue, Jun 14, 2022 at 12:52:23AM +0000, Zhang, Qiang1 wrote: > On Mon, Jun 13, 2022 at 04:42:07PM -0700, Kees Cook wrote: > > On Mon, Jun 13, 2022 at 10:36:07AM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot has tested the proposed patch and the reproducer did not trigger any issue: > > > > > > Reported-and-tested-by: > > > syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com > > > > Looks like the patch solved the reproducer. :) > > >For one of the two possible ways to make the bug happen. ;-) > > > >Still, good on Qiang for identifying one of the paths! Not just anyone can do that. > > Thanks Paul, yes this patch can solved the reproducer and I also test it. > > I compiled "bpf_test" according to the c file in the following link > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=148207bff00000 > > Not apply this patch, this calltrace reproduce > > root@qemux86-64:/# ./bpf_test > ^C > root@qemux86-64:/# dmesg > [ 147.017232] ------------[ cut here ]------------ [ 147.017234] > WARNING: CPU: 3 PID: 21586 at kernel/rcu/tasks.h:1664 > exit_tasks_rcu_finish+0xbf/0x100 [ 147.017245] Modules linked in: > [ 147.017249] CPU: 3 PID: 21586 Comm: bpf_test Not tainted > 5.19.0-rc1-next-20220610-yoctodev-standard #204 [ 147.017253] > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS > rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 [ 147.017256] > RIP: 0010:exit_tasks_rcu_finish+0xbf/0x100 > [ 147.017261] Code: 03 00 00 85 c0 75 59 f0 83 44 24 fc 00 49 8d bc > 24 41 03 00 00 e8 21 09 2b 00 41 0f b6 84 24 41 03 00 00 83 e0 01 08 > d8 74 11 <0f> 8 [ 147.017264] RSP: 0018:ffff88810ccd7af0 EFLAGS: > 00010202 [ 147.017268] RAX: 0000000000000001 RBX: 0000000000000201 > RCX: ffffffff897ab52f [ 147.017271] RDX: 1ffff1102181d7c8 RSI: > 0000000000000000 RDI: ffff88810c0ebe41 [ 147.017274] RBP: > ffff88810ccd7b08 R08: ffffffff897ab510 R09: 0000000000000000 [ > 147.017277] R10: ffffffff8c407bbf R11: 0000000000000000 R12: > ffff88810c0ebb00 [ 147.017279] R13: ffff88810c0ebe38 R14: > ffff88810ccd7b78 R15: ffff88810ccd76b0 [ 147.017282] FS: > 0000000000000000(0000) GS:ffff88815a000000(0000) knlGS:0000000000000000 [ 147.017287] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 147.017289] CR2: 0000000000000000 CR3: 000000011ac16000 CR4: 00000000001506e0 [ 147.017292] Call Trace: > [ 147.017294] <TASK> > [ 147.017297] do_exit+0xe9a/0x13a0 > [ 147.017305] ? mm_update_next_owner+0x450/0x450 [ 147.017309] ? > lock_downgrade+0x410/0x410 [ 147.017313] ? > lock_contended+0x790/0x790 [ 147.017317] ? > rcu_read_lock_held_common+0x1e/0x60 > [ 147.017324] do_group_exit+0x71/0x150 [ 147.017329] > get_signal+0x1319/0x1340 [ 147.017334] ? > futex_wait_setup+0x180/0x180 [ 147.017341] ? > exit_signals+0x4c0/0x4c0 [ 147.017345] ? futex_wake+0x29e/0x2e0 [ > 147.017351] arch_do_signal_or_restart+0x9c/0xc60 > [ 147.017357] ? rcu_read_lock_sched_held+0x60/0xd0 > [ 147.017361] ? rcu_read_lock_bh_held+0xb0/0xb0 [ 147.017367] ? > get_sigframe_size+0x20/0x20 [ 147.017371] ? do_futex+0x1a2/0x240 [ > 147.017375] ? __ia32_sys_get_robust_list+0x240/0x240 > [ 147.017378] ? __context_tracking_exit+0x91/0xa0 [ 147.017385] ? > lock_downgrade+0x410/0x410 [ 147.017390] ? > __x64_sys_futex+0x125/0x2b0 [ 147.017393] ? > rcu_read_lock_held_common+0x1e/0x60 > [ 147.017399] ? lockdep_hardirqs_on_prepare+0x13/0x230 > [ 147.017403] ? exit_to_user_mode_prepare+0x151/0x240 > [ 147.017409] exit_to_user_mode_prepare+0x16c/0x240 > [ 147.017415] syscall_exit_to_user_mode+0x1e/0x70 > [ 147.017419] do_syscall_64+0x50/0x90 [ 147.017423] > entry_SYSCALL_64_after_hwframe+0x46/0xb0 > [ 147.017427] RIP: 0033:0x7f780e668fbd [ 147.017431] Code: Unable to > access opcode bytes at RIP 0x7f780e668f93. > [ 147.017433] RSP: 002b:00007f780e55bd48 EFLAGS: 00000246 ORIG_RAX: > 00000000000000ca [ 147.017437] RAX: fffffffffffffe00 RBX: > 00007f780e55c640 RCX: 00007f780e668fbd [ 147.017440] RDX: > 0000000000000000 RSI: 0000000000000080 RDI: 000055ed9f3a8088 [ > 147.017442] RBP: 00007f780e55bd60 R08: 0000000100000001 R09: > 0000000100000001 [ 147.017445] R10: 0000000000000000 R11: > 0000000000000246 R12: fffffffffffffeb0 [ 147.017447] R13: > 0000000000000000 R14: 00007ffe5dcf20a0 R15: 00007f780e53c000 [ > 147.017455] </TASK> [ 147.017458] irq event stamp: 0 [ 147.017460] > hardirqs last enabled at (0): [<0000000000000000>] 0x0 [ 147.017463] > hardirqs last disabled at (0): [<ffffffff896b5990>] > copy_process+0xe30/0x35f0 [ 147.017467] softirqs last enabled at > (0): [<ffffffff896b5990>] copy_process+0xe30/0x35f0 [ 147.017470] > softirqs last disabled at (0): [<0000000000000000>] 0x0 [ 147.017473] > ---[ end trace 0000000000000000 ]--- > > Apply this patch , this problem not reproduce. > >Thank you very much! May I apply your Tested-by? Thanks, I am very willing > > Thanx, Paul > Thanks > Zqiang > > > > > Thanx, Paul > > > > > Tested on: > > > > > > commit: 6d0c8068 Add linux-next specific files for 20220610 > > > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20220610 > > > console output: > > > https://syzkaller.appspot.com/x/log.txt?x=12d068eff00000 > > > kernel config: > > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641 > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > patch: https://syzkaller.appspot.com/x/patch.diff?x=147f47c8080000 > > > > > > Note: testing is done by a robot and is best-effort only. > > > > You can see the dashboard link above for testing details... > > > > -- > > Kees Cook
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