[PATCH] rcu: Fix kernel stack overflow caused by kprobe on rcu_irq_enter_check_tick()

[Zheng Yejian]

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.

[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@xxxxxxxxxxxxxxx
Fixes: aaf2bc50df1f ("rcu: Abstract out rcu_irq_enter_check_tick() from rcu_nmi_enter()")
Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
---
 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