Commit 91542863abad for kernel

commit 91542863abade2fd4f2b361991f5386ad9d19c8c
Author: Hui Su <sh_def@163.com>
Date:   Fri Aug 7 23:41:46 2026 +0800

    ring-buffer: Fix crash passing ERR_PTR to kthread_stop()

    In test_ringbuffer()'s out_free cleanup loop, the check
    `!rb_threads[cpu]` only catches NULL entries and misses entries that
    hold an ERR_PTR.

    rb_threads[] is static, so unassigned slots are NULL. But when
    kthread_run_on_cpu() fails for a cpu, it stores ERR_PTR(-ENOMEM) (or
    -EINTR) in rb_threads[cpu] before the creation loop jumps to out_free.
    That entry is non-NULL, so the old `!ptr` check does not break, and the
    cleanup proceeds to call kthread_stop() on the ERR_PTR. kthread_stop()
    then dereferences the bogus pointer, crashing the kernel during the
    late_initcall self-test.

    crash logs:
      BUG: kernel NULL pointer dereference, address: 000000000000001c
      Oops: 0002 [#1] SMP NOPTI
      CPU: 1 PID: 1 Comm: swapper/0 Not tainted 7.2.0-rc6-dirty #7 PREEMPT(lazy)
      RIP: 0010:kthread_stop+0x2e/0x220
      RBX: fffffffffffffff4
      CR2: 000000000000001c
      Call Trace:
       <TASK>
       test_ringbuffer+0x1ec/0x650
       do_one_initcall+0x6c/0x2c0
       kernel_init_freeable+0x21d/0x420
       kernel_init+0x15/0x1c0
       ret_from_fork+0x21b/0x320
       </TASK>
      Kernel panic - not syncing: Fatal exception

    Cc: stable@vger.kernel.org
    Fixes: 64ed3a049e3e ("ring-buffer: make use of the helper function kthread_run_on_cpu()")
    Link: https://patch.msgid.link/20260807154145.2846521-2-sh_def@163.com
    Signed-off-by: Hui Su <sh_def@163.com>
    Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
    Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 760a00e8505c..2667992f0aa2 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -8217,7 +8217,7 @@ static __init int test_ringbuffer(void)

  out_free:
 	for_each_online_cpu(cpu) {
-		if (!rb_threads[cpu])
+		if (IS_ERR_OR_NULL(rb_threads[cpu]))
 			break;
 		kthread_stop(rb_threads[cpu]);
 	}