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Date: Fri, 2 Dec 2022 17:54:48 +0800
From: Zheng Yejian <zhengyejian1@...wei.com>
To: <paulmck@...nel.org>
CC: <frederic@...nel.org>, <quic_neeraju@...cinc.com>,
<josh@...htriplett.org>, <rostedt@...dmis.org>,
<mathieu.desnoyers@...icios.com>, <jiangshanlai@...il.com>,
<joel@...lfernandes.org>, <rcu@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rcu: Fix kernel stack overflow caused by kprobe on
rcu_irq_enter_check_tick()
On 2022/11/22 03:57, Paul E. McKenney wrote:
> On Sat, Nov 19, 2022 at 12:00:49PM +0800, Zheng Yejian wrote:
>> Register kprobe on __rcu_irq_enter_check_tick() can cause kernel stack
>> overflow [1]. This issue is first found in v5.10 and can be reproduced
>> by enabling CONFIG_NO_HZ_FULL and doing like:
>> # cd /sys/kernel/debug/tracing/
>> # echo 'p:mp1 __rcu_irq_enter_check_tick' >> kprobe_events
>> # echo 1 > events/kprobes/enable
>>
>> So __rcu_irq_enter_check_tick() should not be kprobed, mark it as noinstr.
>
> Good catch!
>
> I am inclined to queue this, but noticed that one of its callers need
> it to be noinstr but that the others do not.
>
> Need noinstr:
>
> o enter_from_kernel_mode() -> __enter_from_kernel_mode() ->
> rcu_irq_enter_check_tick() -> __rcu_irq_enter_check_tick()
>
> Doesn't need noinstr:
>
> o ct_nmi_enter() -> rcu_irq_enter_check_tick() ->
> __rcu_irq_enter_check_tick(), courtesy of the call to
> instrumentation_begin() in ct_nmi_enter() that precedes the call
> to rcu_irq_enter_check_tick().
>
> o irqentry_enter() -> rcu_irq_enter_check_tick() ->
> __rcu_irq_enter_check_tick(), courtesy of the call to
> instrumentation_begin() in irqentry_enter() that precedes the
> call to rcu_irq_enter_check_tick().
>
> Is tagging __rcu_irq_enter_check_tick() with noinstr as
> proposed in this patch the right thing to do, or should there
> be calls to instrumentation_begin() and instrumentation_end() in
> enter_from_kernel_mode()? Or something else entirely?
I have tried the calls to instrumentation_{begin,end}() in
enter_from_kernel_mode(), see [1]. But this problem can still be
reproduced, maybe more complete calltrace info [2] is needed for
analyzing.
Did I add the instrumentation_{begin,end}() in wrong place or is there
other caller need noinstr?
[1]
diff --git a/arch/arm64/kernel/entry-common.c
b/arch/arm64/kernel/entry-common.c
index 27369fa1c032..deed5a0941d3 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -49,7 +49,9 @@ static __always_inline void
__enter_from_kernel_mode(struct pt_regs *regs)
}
lockdep_hardirqs_off(CALLER_ADDR0);
+ instrumentation_begin();
rcu_irq_enter_check_tick();
+ instrumentation_end();
trace_hardirqs_off_finish();
}
[2]
[ 48.921197] Call trace:
[ 48.921241] dump_backtrace+0xf8/0x108
[ 48.921358] show_stack+0x20/0x48
[ 48.921418] dump_stack_lvl+0x68/0x84
[ 48.921477] dump_stack+0x1c/0x38
[ 48.921530] panic+0x214/0x404
[ 48.921598] add_taint+0x0/0xf0
[ 48.921657] panic_bad_stack+0x144/0x160
[ 48.921715] handle_bad_stack+0x38/0x58
[ 48.921774] __bad_stack+0x78/0x7c
[ 48.921825] __rcu_irq_enter_check_tick+0x0/0x1b8
[ 48.921886] arm64_enter_el1_dbg.isra.0+0x14/0x20
[ 48.921949] el1_dbg+0x2c/0x90
[ 48.922001] el1h_64_sync_handler+0xcc/0xe8
[ 48.922061] el1h_64_sync+0x64/0x68
[ 48.922112] __rcu_irq_enter_check_tick+0x0/0x1b8
[...]
[ 48.938382] __rcu_irq_enter_check_tick+0x0/0x1b8
[ 48.938441] arm64_enter_el1_dbg.isra.0+0x14/0x20
[ 48.938500] el1_dbg+0x2c/0x90
[ 48.938549] el1h_64_sync_handler+0xcc/0xe8
[ 48.938607] el1h_64_sync+0x64/0x68
[ 48.938656] __rcu_irq_enter_check_tick+0x0/0x1b8
[ 48.938715] arm64_enter_el1_dbg.isra.0+0x14/0x20
[ 48.938778] el1_dbg+0x2c/0x90
[ 48.938829] el1h_64_sync_handler+0xcc/0xe8
[ 48.938887] el1h_64_sync+0x64/0x68
[ 48.938936] __rcu_irq_enter_check_tick+0x0/0x1b8
[ 48.938995] arm64_enter_el1_dbg.isra.0+0x14/0x20
[ 48.939054] el1_dbg+0x2c/0x90
[ 48.939105] el1h_64_sync_handler+0xcc/0xe8
[ 48.939164] el1h_64_sync+0x64/0x68
[ 48.939215] __rcu_irq_enter_check_tick+0x0/0x1b8
[ 48.939274] el1_interrupt+0x28/0x60
[ 48.939327] el1h_64_irq_handler+0x18/0x28
[ 48.939385] el1h_64_irq+0x64/0x68
[ 48.939434] __asan_load8+0x54/0xa8
[ 48.939500] __ftrace_set_clr_event_nolock+0x6c/0x198
[ 48.939563] __ftrace_set_clr_event+0x58/0x80
[ 48.939618] system_enable_write+0x144/0x178
[ 48.939673] vfs_write+0x174/0x738
[ 48.939734] ksys_write+0xd0/0x188
[ 48.939791] __arm64_sys_write+0x4c/0x60
[ 48.939851] invoke_syscall+0x64/0x180
[ 48.939921] el0_svc_common.constprop.0+0x84/0x160
[ 48.939996] do_el0_svc+0x48/0xf8
[ 48.940062] el0_svc+0x34/0xd0
[ 48.940114] el0t_64_sync_handler+0xb8/0xc0
[ 48.940173] el0t_64_sync+0x18c/0x190
[ 48.940872] SMP: stopping secondary CPUs
[ 48.942844] Kernel Offset: 0x2d9499c00000 from 0xffff800008000000
[ 48.942938] PHYS_OFFSET: 0xffffaa9840000000
[ 48.942999] CPU features: 0x00000,00d00080,0000421b
[ 48.943387] Memory Limit: none
>
> Thoughts?
Sorry, I have no more idea :-(
>
> Thanx, Paul
>
>> [1]
>> Insufficient stack space to handle exception!
>> Insufficient stack space to handle exception!
>> [...]
>> Kernel panic - not syncing: kernel stack overflow
>> CPU: 3 PID: 34 Comm: migration/3 Not tainted
>> 6.1.0-rc5-00884-g84368d882b96 #2
>> Hardware name: linux,dummy-virt (DT)
>> Stopper: multi_cpu_stop+0x0/0x228 <- __stop_cpus.constprop.0+0xa4/0x100
>> Call trace:
>> dump_backtrace+0xf8/0x108
>> show_stack+0x20/0x48
>> dump_stack_lvl+0x68/0x84
>> dump_stack+0x1c/0x38
>> panic+0x214/0x404
>> add_taint+0x0/0xf0
>> panic_bad_stack+0x144/0x160
>> handle_bad_stack+0x38/0x58
>> __bad_stack+0x78/0x7c
>> el1h_64_sync_handler+0x4/0xe8
>> __rcu_irq_enter_check_tick+0x0/0x1b8
>> arm64_enter_el1_dbg.isra.0+0x14/0x20
>> el1_dbg+0x2c/0x90
>> el1h_64_sync_handler+0xcc/0xe8
>> el1h_64_sync+0x64/0x68
>> __rcu_irq_enter_check_tick+0x0/0x1b8
>> arm64_enter_el1_dbg.isra.0+0x14/0x20
>> el1_dbg+0x2c/0x90
>> el1h_64_sync_handler+0xcc/0xe8
>> el1h_64_sync+0x64/0x68
>> __rcu_irq_enter_check_tick+0x0/0x1b8
>> arm64_enter_el1_dbg.isra.0+0x14/0x20
>> el1_dbg+0x2c/0x90
>> el1h_64_sync_handler+0xcc/0xe8
>> el1h_64_sync+0x64/0x68
>> __rcu_irq_enter_check_tick+0x0/0x1b8
>> arm64_enter_el1_dbg.isra.0+0x14/0x20
>> el1_dbg+0x2c/0x90
>> el1h_64_sync_handler+0xcc/0xe8
>> el1h_64_sync+0x64/0x68
>> __rcu_irq_enter_check_tick+0x0/0x1b8
>> arm64_enter_el1_dbg.isra.0+0x14/0x20
>> el1_dbg+0x2c/0x90
>> el1h_64_sync_handler+0xcc/0xe8
>> el1h_64_sync+0x64/0x68
>> __rcu_irq_enter_check_tick+0x0/0x1b8
>> [...]
>>
>> Cc: stable@...r.kernel.org
>> Fixes: aaf2bc50df1f ("rcu: Abstract out rcu_irq_enter_check_tick() from rcu_nmi_enter()")
>> Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
>> ---
>> kernel/rcu/tree.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
>> index 93416afebd59..68230f02cfb7 100644
>> --- a/kernel/rcu/tree.c
>> +++ b/kernel/rcu/tree.c
>> @@ -631,7 +631,7 @@ void rcu_irq_exit_check_preempt(void)
>> * controlled environments, this function allows RCU to get what it
>> * needs without creating otherwise useless interruptions.
>> */
>> -void __rcu_irq_enter_check_tick(void)
>> +noinstr void __rcu_irq_enter_check_tick(void)
>> {
>> struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
>>
>> --
>> 2.25.1
>>
--
Best regards,
Zheng Yejian
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