From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 331AB27FD4B; Thu, 4 Sep 2025 20:28:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757017682; cv=none; b=o9ilnL6ewVz5dsO2KkNRf0ORnybJiG25ci8XBZY4Kbuc4ybGVxVOAm7MmUFBXGXapI4AGIg5Y/jmB+4jKjS2o+0GRMXI7ETtgQgY/l5g0ffHC0qkaijz1IdaGLXBB5cmHftqpy1Cl5qj16eKCb1t+A5lutz65FJ5dVwfLU6iHVI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757017682; c=relaxed/simple; bh=nUxw2F99A5SVU4pIGmbQ8xdl9OE4cjF0PUxIIjz+/ZU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=To/SXsPD3W8T+n48jtxHN3Oe6XnwQXx43DDkcvc0wYuDgYDBoQYvtts8d8JxbnTAQjecYvUyi/so1iBWF0GoIiNrbEqQrmEaKoguJJH/+fPaD9DqPAagTYGxjay0Weh3di8xNeKrFaV0+8pruM9aHN2W85Y7QAAztpKcJZkc5oI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z06lSuML; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z06lSuML" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C169C4CEF0; Thu, 4 Sep 2025 20:28:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757017680; bh=nUxw2F99A5SVU4pIGmbQ8xdl9OE4cjF0PUxIIjz+/ZU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Z06lSuML12fVHl12/wXUtMCeD+Vb3uDHkTwYsUMqCztx6f2/ZBKMmMXgqFKdP1rFL op3vovSeH60QiPTjRkbdBKGhNGcfDW6JNIYkaGFv5kUrLihMVoSBbUIogiFG2VDEqe Wj04RjgVMTRc5TwvhchbX6Yj3te/bcpHVMk8kWakKwJsd7ygmfkVxRlKrJQalusCAr QA9p9uYc6HlyEE61Mby2EdXTUEqD6cw8oWZ9vocLuuVeTTIUcxeW0JGsrBD01zjoDs f9xIMhkTK4B0wjRAIkTsWcIwUVYUrJ/JaSocAAUY2+7W+JvoJ3gRfSbahodNWQXbGc umcCFTdmNPYkg== Date: Thu, 4 Sep 2025 10:27:59 -1000 From: Tejun Heo To: Andrea Righi Cc: David Vernet , Changwoo Min , Christian Loehle , Jake Hillion , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 sched_ext/for-6.18] sched_ext: Fix NULL dereference in scx_bpf_cpu_rq() warning Message-ID: References: <20250904182348.107835-1-arighi@nvidia.com> Precedence: bulk X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250904182348.107835-1-arighi@nvidia.com> On Thu, Sep 04, 2025 at 08:23:48PM +0200, Andrea Righi wrote: > When printing the deprecation warning for scx_bpf_cpu_rq(), we may hit a > NULL pointer dereference if the kfunc is called before a BPF scheduler > is fully attached, for example, when invoked from a BPF timer or during > ops.init(): > > [ 50.752775] BUG: kernel NULL pointer dereference, address: 0000000000000331 > ... > [ 50.764205] RIP: 0010:scx_bpf_cpu_rq+0x30/0xa0 > ... > [ 50.787661] Call Trace: > [ 50.788398] > [ 50.789061] bpf_prog_08f7fd2dcb187aaf_wakeup_timerfn+0x75/0x1a8 > [ 50.792477] bpf_timer_cb+0x7e/0x140 > [ 50.796003] hrtimer_run_softirq+0x91/0xe0 > [ 50.796952] handle_softirqs+0xce/0x3c0 > [ 50.799087] run_ksoftirqd+0x3e/0x70 > [ 50.800197] smpboot_thread_fn+0x133/0x290 > [ 50.802320] kthread+0x115/0x220 > [ 50.804984] ret_from_fork+0x17a/0x1d0 > [ 50.806920] ret_from_fork_asm+0x1a/0x30 > [ 50.807799] > > Fix this by only printing the warning once the scheduler is fully > registered. > > Fixes: 5c48d88fe0049 ("sched_ext: deprecation warn for scx_bpf_cpu_rq()") > Cc: Christian Loehle > Signed-off-by: Andrea Righi Applied to sched_ext/for-6.18. Thanks. -- tejun