From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yx1-f51.google.com (mail-yx1-f51.google.com [74.125.224.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83B9E383304 for ; Tue, 12 May 2026 02:07:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.224.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778551632; cv=none; b=cfFfDLthIVo6eDdA3vbm9W6HII0gql7uWRp8M6SyS3IyuGFZnB5c0JsCf8nZIjWgRCNBb54fkeC7NmX7goeTlFymb4sBI1kTe7wPhVxecyU71+zLQjN6KT9Xqm9wYkcN23n/V9Zbmeqb3oEcukGhQKnWIqPl+fyefw6MRog+wag= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778551632; c=relaxed/simple; bh=uCnPTczXRGCjJkasxe+ExAASvngVWa567A59zopNH78=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LrTYYC68mekSgQ8o5USHH5WgFsnBIiMyt8s3O/pykdHmDtRMygNQ5ngRne+8oBl8GAq+1JJkLC/+q+8htzom8Xdd/DEC9n/94jXojrhQ1px3ZESG2zM0K6xzmB1ZOVPn50NHY9w+9NKHRd0M0Z6ndTJwd6/oSyzNCMMZOqKWqQA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=qEX44jXZ; arc=none smtp.client-ip=74.125.224.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="qEX44jXZ" Received: by mail-yx1-f51.google.com with SMTP id 956f58d0204a3-65c364b893aso4823289d50.0 for ; Mon, 11 May 2026 19:07:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1778551630; x=1779156430; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=VMuUQCVEJE6aMa+W2DJMi+Yspl9yx7h60YzqRdzSdYs=; b=qEX44jXZoqKunEwLInD4vegNkHUxXDMpLjzhapkeKedn0NWiljYo6bSn86utQGiYoO 4gEDC694xsrmFZ8tAjwJSai0mhMoRVufGfdeRusiB9nXlWh6w+o0IblRrljigm7b4jsp svoGYUJIAfJ3z5gtf1m5rPXBw0ONg62/Fc016aQOuRDwDzJuO4yKSix6HGB8wb97Yb65 k6+6nwiDO7KbFKazEcFPr1VVqnn8gZXMOKmvB4rL7Ce++ScCceLQCKq/oHeaTF/ZEQNl i3KJbLJcNNJQQK9x8aWlVQ1GAPJMoogfZtPzvDkh8M2JRCtIki6OVG2XPYfbRwlyMIbP jWSA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778551630; x=1779156430; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=VMuUQCVEJE6aMa+W2DJMi+Yspl9yx7h60YzqRdzSdYs=; b=dGqHrAdzgn/r9dF4fZ2kmOVOwuGANgJnUS/5RTXgAWlwkHjO9akjLekLHlyXC7sP6m pdQzUvlO9lRUUo/qzShlKIupTHAvHR4MkWNe9AehgXml1Hxut3g51UR8Hogq2dor12Cr KNHtzUUydi9GqnINI4KUS9DIgwdWuVTybwj49xTTy1r2RZAHJ496A5eR9k3wcNwLAGEh 2aDofOnmeKm5HufpVcRr/owj7EksIb8ULgUymVZol6GFOvLZ0hDVTyYCyJPWRHDlwjZQ sSChitbr3AXFVeRxwjbJ0t6HDPe3I4rXqlwq9bAnhs53uJ0NTDVbrDb3qlDAU7qs9ozT oGog== X-Forwarded-Encrypted: i=1; AFNElJ9yDlkzArSrNmL2e/ynf8kONCqzIna+03fpzMqoJfIOfLR7LFLHHwQmmFIqzitW6aJTjUM=@vger.kernel.org X-Gm-Message-State: AOJu0YxEDCBTlJyaBO56FJPZedHn4Yk5oaz7NInQ2DdDtaVheIOZGOxW BMNTOAGlPXQg5rcsUa8ejdwMhA41Ed7cOXboYiVH91Fkq/skLh6oJrIf X-Gm-Gg: Acq92OF/K1zMKOGdlVJK1IS+xvjZFgX/4ZLazjBbZ1l5rCcgqleI2cON+tKTKdMeLZv kdrdYVJTxwwK+EtG6CSGy/zK5ceNtlj89B7aDPUytPT+dB/oNkB9ebKFzhaYrxcxB7ByjEUKU53 JTkhu2YabI+wzBfmQdcwD10I2hVX6D9C7gzjr+8FW39NvbE+1Qbe5R1yxtl/8zBezharXc0ck4i d6H8E2V7CLuE0MXTl4wHQ2fDiXl+8lVCUhx1cCLDtUANBFZJWw9P9U5sH9/mPBG57fHVeMc4rKN wzyRZLRahRZvHTmeLm4FYjRTwLuRbXA7M+4BwXVrwuYzdh93/mduCAJ3nlT2pFLJRTq17psBYn2 PZ9cKuMtu0ECJHJYiHCeJCbiK59tbcLTn6R0ndphlMDMmkkom+64XRNc9etIbfISnTO50GkYeyd q0LTAGSDGfa+cdsmYQuQvORD2OcV6c3mrEDbhu4+BJpbEn8GY3Fow8Ew28jA== X-Received: by 2002:a05:690e:1282:b0:65c:ed33:bda5 with SMTP id 956f58d0204a3-65d94901e32mr16907981d50.0.1778551630402; Mon, 11 May 2026 19:07:10 -0700 (PDT) Received: from zenbox ([2600:1700:18fb:6011:6d1b:2c6f:d117:7f3e]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7bd66019105sm159044777b3.0.2026.05.11.19.07.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 19:07:09 -0700 (PDT) Date: Mon, 11 May 2026 22:07:09 -0400 From: Justin Suess To: Alexei Starovoitov Cc: Kumar Kartikeya Dwivedi , sashiko@lists.linux.dev, bpf Subject: Re: [bpf-next v3 1/2] bpf: Offload kptr destructors that run from NMI Message-ID: References: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, May 11, 2026 at 06:55:50PM -0700, Alexei Starovoitov wrote: > On Mon May 11, 2026 at 6:46 PM PDT, Kumar Kartikeya Dwivedi wrote: > > On Tue, 12 May 2026 at 03:43, Justin Suess wrote: > >> > >> On Mon, May 11, 2026 at 10:10:07PM +0200, Kumar Kartikeya Dwivedi wrote: > >> > On Mon, 11 May 2026 at 19:29, Alexei Starovoitov > >> > wrote: > > There is no deferral here. I'm saying that we just cancel for timer, > > wq, task work, and leave other fields as is. So we don't have active > > work pending for async items. > > > > So as long as the item keeps getting recycled in the allocator, we > > don't free these fields. Once the memalloc is destroyed, the dtor runs > > in a known safe context where we can assume bpf_obj_free_fields won't > > deadlock or run into any problems. > > So the plan is to do > if (in_nmi()) && case BPF_KPTR* | BPF_LIST_HEAD | BPF_RB_ROOT > just ignore it? > And no other changes anywhere at all? > > That would be too good to be true :) I guess the last question I have is what would prevent an xchg() out of a map on a recycled kptr from causing a UAF?