Re: [tip:perf/core] [perf] da916e96e2: BUG:KASAN:null-ptr-deref_in_put_event

[Peter Zijlstra <peterz@infradead.org>]

On Mon, Apr 14, 2025 at 09:59:25AM +0800, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed "BUG:KASAN:null-ptr-deref_in_put_event" on:
> 
> commit: da916e96e2dedcb2d40de77a7def833d315b81a6 ("perf: Make perf_pmu_unregister() useable")
> https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git perf/core
> 
> [test failed on linux-next/master 29e7bf01ed8033c9a14ed0dc990dfe2736dbcd18]
> 
> in testcase: trinity
> version: trinity-x86_64-ba2360ed-1_20241228
> with following parameters:
> 
> 	runtime: 300s
> 	group: group-02
> 	nr_groups: 5
> 
> 
> 
> config: x86_64-randconfig-078-20250407
> compiler: clang-20
> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> 
> (please refer to attached dmesg/kmsg for entire log/backtrace)
> 
> 
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <oliver.sang@intel.com>
> | Closes: https://lore.kernel.org/oe-lkp/202504131701.941039cd-lkp@intel.com
> 

Does this help?

---
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2eb9cd5d86a1..528b679aaf7e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5687,7 +5687,7 @@ static void put_event(struct perf_event *event)
 	_free_event(event);
 
 	/* Matches the refcount bump in inherit_event() */
-	if (parent)
+	if (parent && parent != EVENT_TOMBSTONE)
 		put_event(parent);
 }