From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7903B3A0B13; Sun, 9 Aug 2026 02:32:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786242739; cv=none; b=ab1cSJMu3/IZ4abSoeLdxL/c1Exa8+76LqzPQr900a6G9cb4ow89g/w4JdjNmSpGh39qM6tHr90g1Yhv9s9aqsIStBUi5MYaPsZ+YKAqd6JCi+cmSvW+O5tvi0VIDO3fch7As13WFcMfReMizzggzubcfF9GC3VmvGA/L8DILw0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786242739; c=relaxed/simple; bh=aKVMLffV36JJyvmlxsMLg1QEYQKPju/acbqSOYLKtnU=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=HDsVeCjdBy0ANxrT0+nOeHIqR02kA+SxjCY13J5SsyrkT2/pKCMwSFti197g4Lx9t1547RmKzg319+Ct0iKDQzD39lOPzgxBBOPSLFJkPRdkjxSN4q/D3qLJtvp/FQWeSqJinEYhzGYhjCcFFyYxpQB93IhWBmNMMUcOT/JEX+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YTIi23l8; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YTIi23l8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5E0C1F000E9; Sun, 9 Aug 2026 02:32:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786242736; bh=vrM2+TD+0MkuWqm0kWaBZvs35CJnjmmoRSUJZIkU/3k=; h=Date:From:To:Cc:Subject:References; b=YTIi23l8zxd0bZTQ+AotYTkZ5w+lp4pe2P2ZGI7pFj9qgUPBdigGN2afvd4oy56B7 vvWSSktG9zdh1Xxfj0pm7deKtN1edEoK6QMlsmk6WKTyvdmX6M61sPGMC2ncDp+gG/ AJvxsEnlgC5D87fOFvKYEB5uuh5AQdPGuqy+bWB5BXDjG2+W6awK0sTSePVhZj7Gkz yZ0VXdrqPTsK+Q+5V6Qu4hBIY1XM9IhSc0qWlBmTGpf8RdqYKeaKSfaUSmFMFmRS5W TABROXsGypppdIbrATQkCz2yd3apKJUTo7fQ7o+Sdv19Er1AFWvZyyMSOuww7iCfbn CCUsTQZ2Ag9nw== Received: from rostedt by gandalf with local (Exim 4.99.4) (envelope-from ) id 1wstKp-00000001N8B-0vAX; Sat, 08 Aug 2026 22:32:23 -0400 Message-ID: <20260809023223.100369362@kernel.org> User-Agent: quilt/0.69 Date: Sat, 08 Aug 2026 22:31:56 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , stable@vger.kernel.org, Hui Su , Vincent Donnefort Subject: [for-linus][PATCH 12/12] ring-buffer: Fix crash passing ERR_PTR to kthread_stop() References: <20260809023144.852271250@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: Hui Su 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: test_ringbuffer+0x1ec/0x650 do_one_initcall+0x6c/0x2c0 kernel_init_freeable+0x21d/0x420 kernel_init+0x15/0x1c0 ret_from_fork+0x21b/0x320 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 Reviewed-by: Vincent Donnefort Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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]); } -- 2.53.0