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 7011018035 for ; Thu, 24 Oct 2024 00:56:41 +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=1729731401; cv=none; b=C0jjQFcEBL6QcKewTKfESnPvLfqkMSzI0Rde/MLKjk57GCemN3ABXxMMrpr9HGvxsKz1VvGsyBufuTvII+u+0VLwVTiKNeF4LDydlilxcVwYT/sGiq90RMcREaXsxJTjZVyIEmLTcAvX0jKmBCaA7h6Uv4/PfUjIsknrcLHaiWY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729731401; c=relaxed/simple; bh=SQfxKjWkjYYEdeECVK8wdsyQOhnFnmkfg4+vuiNOick=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JIN5BnxtZOiduRex/nr7wqzu+NfLKNdBz9BWk2Qi7QjuzvYgNx1UZlao+fmwfj5pX5ZdNtW7ovSXZSGaxwwXrsV7bbaCwKRU97Zub2WVo8VUE12+/s8qvWcKq3LPPsgJ6GcDQwxdVcuv1ve8Dl7t9pknwqGjSSsCeWWJQ8jTE5U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=M2GxXa68; 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="M2GxXa68" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D877AC4CEC6; Thu, 24 Oct 2024 00:56:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729731401; bh=SQfxKjWkjYYEdeECVK8wdsyQOhnFnmkfg4+vuiNOick=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M2GxXa68w8ovQvsQGavOSEnqoeYM0JRRYr2UP6sOIUvqBqS7iqg9e7nwyq5UjWcwJ mLjIcWy3Y3al7WM353AlBbI5KNKCNkw5PNCAvCgrN/g2dXg6CpViAwSQzPM4QvSSho SH3Ry1CqP6aMShApT/bzPodYnisv5ze16i5gImEJqLYPZyiHcKZ0N/rBiX7tissPbb TCCuzrdT0SenUENDcHGHkCsGzyYpNW35xECD7m+D4hC8cIXFuWxp5PcnVVKjOWcArH J4A5Dc3OOffnEpZSvzUKxiErFYguxzK8oemlTNhA7Ew+trmWqWmbmdTWlFgbJt9toa XfT7bdnPXM6QA== Date: Wed, 23 Oct 2024 14:56:40 -1000 From: Tejun Heo To: Alexei Starovoitov Cc: Martin KaFai Lau , Yonghong Song , bpf , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Kernel Team , Martin KaFai Lau Subject: Re: [PATCH bpf-next v6 3/9] bpf: Support private stack for struct ops programs Message-ID: References: <20241020191341.2104841-1-yonghong.song@linux.dev> <20241020191400.2105605-1-yonghong.song@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Oct 23, 2024 at 04:07:49PM -0700, Alexei Starovoitov wrote: > On Wed, Oct 23, 2024 at 2:00 PM Tejun Heo wrote: > > > > Hello, > > > > On Tue, Oct 22, 2024 at 01:19:58PM -0700, Alexei Starovoitov wrote: > > > > The __nullable argument tagging request was originally from sched_ext but I also > > > > don't see its usage in-tree for now. > > > > > > ok. Let's sync up with Tejun whether they have plans to use it. > > > > Yeah, in sched_ext_ops.dispatch(s32 cpu, struct task_struct *prev), @prev > > can be NULL and right now if a BPF scheduler derefs without checking for > > NULL, it can trigger kernel crash, I think, so it needs __nullable tagging. > > I see. The following should do it: > diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c > index 3cd7c50a51c5..82bef41d7eae 100644 > --- a/kernel/sched/ext.c > +++ b/kernel/sched/ext.c > @@ -5492,7 +5492,7 @@ static int bpf_scx_validate(void *kdata) > static s32 select_cpu_stub(struct task_struct *p, s32 prev_cpu, u64 > wake_flags) { return -EINVAL; } > static void enqueue_stub(struct task_struct *p, u64 enq_flags) {} > static void dequeue_stub(struct task_struct *p, u64 enq_flags) {} > -static void dispatch_stub(s32 prev_cpu, struct task_struct *p) {} > +static void dispatch_stub(s32 prev_cpu, struct task_struct *p__nullable) {} This is a lot neater than the existing workaround: http://lkml.kernel.org/r/Zxma-ZFPKYZDqCGu@slm.duckdns.org Thanks! -- tejun