* [PATCH -tip ] [BUGFIX] kprobes: Skip kretprobe hit in NMI context to avoid deadlock
@ 2014-08-01 8:42 Masami Hiramatsu
2014-08-01 9:48 ` Ananth N Mavinakayanahalli
2014-08-01 11:00 ` Ingo Molnar
0 siblings, 2 replies; 4+ messages in thread
From: Masami Hiramatsu @ 2014-08-01 8:42 UTC (permalink / raw)
To: Ingo Molnar; +Cc: linux-kernel, Ananth N Mavinakayanahalli, David S. Miller
Skip kretprobe hit in NMI context, because if an NMI happens
inside the critical section protected by kretprobe_table.lock
and another(or same) kretprobe hit, pre_kretprobe_handler
tries to lock kretprobe_table.lock again.
Normal interrupts have no problem because they are disabled
with the lock.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
---
kernel/kprobes.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 734e9a7..a537029 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1778,6 +1778,12 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
unsigned long hash, flags = 0;
struct kretprobe_instance *ri;
+ /* To avoid deadlock, prohibit return probing in NMI context */
+ if (in_nmi()) {
+ rp->nmissed++;
+ return 0;
+ }
+
/*TODO: consider to only swap the RA after the last pre_handler fired */
hash = hash_ptr(current, KPROBE_HASH_BITS);
raw_spin_lock_irqsave(&rp->lock, flags);
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH -tip ] [BUGFIX] kprobes: Skip kretprobe hit in NMI context to avoid deadlock
2014-08-01 8:42 [PATCH -tip ] [BUGFIX] kprobes: Skip kretprobe hit in NMI context to avoid deadlock Masami Hiramatsu
@ 2014-08-01 9:48 ` Ananth N Mavinakayanahalli
2014-08-01 11:00 ` Ingo Molnar
1 sibling, 0 replies; 4+ messages in thread
From: Ananth N Mavinakayanahalli @ 2014-08-01 9:48 UTC (permalink / raw)
To: Masami Hiramatsu; +Cc: Ingo Molnar, linux-kernel, David S. Miller
On Fri, Aug 01, 2014 at 08:42:54AM +0000, Masami Hiramatsu wrote:
> Skip kretprobe hit in NMI context, because if an NMI happens
> inside the critical section protected by kretprobe_table.lock
> and another(or same) kretprobe hit, pre_kretprobe_handler
> tries to lock kretprobe_table.lock again.
> Normal interrupts have no problem because they are disabled
> with the lock.
>
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH -tip ] [BUGFIX] kprobes: Skip kretprobe hit in NMI context to avoid deadlock
2014-08-01 8:42 [PATCH -tip ] [BUGFIX] kprobes: Skip kretprobe hit in NMI context to avoid deadlock Masami Hiramatsu
2014-08-01 9:48 ` Ananth N Mavinakayanahalli
@ 2014-08-01 11:00 ` Ingo Molnar
2014-08-02 6:37 ` Masami Hiramatsu
1 sibling, 1 reply; 4+ messages in thread
From: Ingo Molnar @ 2014-08-01 11:00 UTC (permalink / raw)
To: Masami Hiramatsu
Cc: linux-kernel, Ananth N Mavinakayanahalli, David S. Miller
* Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
> Skip kretprobe hit in NMI context, because if an NMI happens
> inside the critical section protected by kretprobe_table.lock
> and another(or same) kretprobe hit, pre_kretprobe_handler
> tries to lock kretprobe_table.lock again.
> Normal interrupts have no problem because they are disabled
> with the lock.
>
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> ---
> kernel/kprobes.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 734e9a7..a537029 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1778,6 +1778,12 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
> unsigned long hash, flags = 0;
> struct kretprobe_instance *ri;
>
> + /* To avoid deadlock, prohibit return probing in NMI context */
> + if (in_nmi()) {
Should be unlikely()?
> + rp->nmissed++;
> + return 0;
In another place in this function we do:
} else {
rp->nmissed++;
raw_spin_unlock_irqrestore(&rp->lock, flags);
}
Is it safe to modify rp-> without locking?
> + }
> +
> /*TODO: consider to only swap the RA after the last pre_handler fired */
Nit: That comment is oddly formatted.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH -tip ] [BUGFIX] kprobes: Skip kretprobe hit in NMI context to avoid deadlock
2014-08-01 11:00 ` Ingo Molnar
@ 2014-08-02 6:37 ` Masami Hiramatsu
0 siblings, 0 replies; 4+ messages in thread
From: Masami Hiramatsu @ 2014-08-02 6:37 UTC (permalink / raw)
To: Ingo Molnar; +Cc: linux-kernel, Ananth N Mavinakayanahalli, David S. Miller
(2014/08/01 20:00), Ingo Molnar wrote:
>
> * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
>
>> Skip kretprobe hit in NMI context, because if an NMI happens
>> inside the critical section protected by kretprobe_table.lock
>> and another(or same) kretprobe hit, pre_kretprobe_handler
>> tries to lock kretprobe_table.lock again.
>> Normal interrupts have no problem because they are disabled
>> with the lock.
>>
>> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
>> Cc: "David S. Miller" <davem@davemloft.net>
>> ---
>> kernel/kprobes.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
>> index 734e9a7..a537029 100644
>> --- a/kernel/kprobes.c
>> +++ b/kernel/kprobes.c
>> @@ -1778,6 +1778,12 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
>> unsigned long hash, flags = 0;
>> struct kretprobe_instance *ri;
>>
>> + /* To avoid deadlock, prohibit return probing in NMI context */
>> + if (in_nmi()) {
>
> Should be unlikely()?
Ah, Indeed.
>
>> + rp->nmissed++;
>> + return 0;
>
> In another place in this function we do:
>
> } else {
> rp->nmissed++;
> raw_spin_unlock_irqrestore(&rp->lock, flags);
> }
>
> Is it safe to modify rp-> without locking?
Yes, rp->nmissed is just for noticing the fault to users,
not for controlling.:) If we need more accurate value, we'd
better make it atomic_t.
Thank you,
>
>> + }
>> +
>> /*TODO: consider to only swap the RA after the last pre_handler fired */
>
> Nit: That comment is oddly formatted.
>
> Thanks,
>
> Ingo
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-08-02 6:37 UTC | newest]
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2014-08-01 8:42 [PATCH -tip ] [BUGFIX] kprobes: Skip kretprobe hit in NMI context to avoid deadlock Masami Hiramatsu
2014-08-01 9:48 ` Ananth N Mavinakayanahalli
2014-08-01 11:00 ` Ingo Molnar
2014-08-02 6:37 ` Masami Hiramatsu
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