From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 26DFEE668B4 for ; Sat, 20 Dec 2025 18:43:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 550126B0088; Sat, 20 Dec 2025 13:43:24 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 507FC6B0089; Sat, 20 Dec 2025 13:43:24 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 433DD6B008A; Sat, 20 Dec 2025 13:43:24 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 3577B6B0088 for ; Sat, 20 Dec 2025 13:43:24 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id C7B8060645 for ; Sat, 20 Dec 2025 18:43:23 +0000 (UTC) X-FDA: 84240722286.09.4F43881 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) by imf25.hostedemail.com (Postfix) with ESMTP id 4DE56A000F for ; Sat, 20 Dec 2025 18:43:20 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=cvY49sZh; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf25.hostedemail.com: domain of roman.gushchin@linux.dev designates 95.215.58.177 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1766256202; a=rsa-sha256; cv=none; b=gngNn/qnRHzFQQcuHaxgGdKyDKR1Lc+LHctlVBtDY4HeyJ2jKot9FNri89dUo9jP40guvn oIr//WkR609seoSHTS59EVjorLqNcP+irIeK7WUPrUSLBtG37lwrsRW+IwBmogd5qmT4uh Uxbao8zevCdKLhxawlrpxtdTZu+zA1Y= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=cvY49sZh; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf25.hostedemail.com: domain of roman.gushchin@linux.dev designates 95.215.58.177 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1766256202; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=oYcEDFt+reXAq8S6HjO2WYSFnT1e9O506FR9izTfXYg=; b=aO0f5WaebmT3niU2EV45pVSLu9v1+tChNzi+31Kio0whsZPNsYAVikMJJsdJR+czmMT+zX W2Z1xmk/MB3Y6Z48m5+YnZtyJ7nNqegnvPd8/ojxE4AMcCwGVx7hrvuYJiA26DOtrqjws6 NWqqFBPEH9AC1jXBxDBSgEctUMG9iMY= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1766256196; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=oYcEDFt+reXAq8S6HjO2WYSFnT1e9O506FR9izTfXYg=; b=cvY49sZhS6fWeTI911eazXNzrmFdqSxRKUzbVC0iI+/hbUFYPVRLxBYhV+omoSJ4qYGCGd T+J+0lOp1MAZbo63six8tvYdFFeqPoxqKxXKCktKgUNxOmiWZSya9Uh9GF3Tdw2JMpv5Ie jjF8ZEi7Y1sfl8nGmdDUXOqELd/STkA= From: Roman Gushchin To: Chris Mason Cc: bot+bpf-ci@kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, inwardvessel@gmail.com, ast@kernel.org, daniel@iogearbox.net, shakeel.butt@linux.dev, mhocko@kernel.org, hannes@cmpxchg.org, andrii@kernel.org, martin.lau@kernel.org, eddyz87@gmail.com, yonghong.song@linux.dev, ihor.solodrai@linux.dev Subject: Re: [PATCH bpf-next v2 5/7] mm: introduce BPF kfunc to access memory events In-Reply-To: (Chris Mason's message of "Sat, 20 Dec 2025 08:19:48 -0500") References: <20251220041250.372179-6-roman.gushchin@linux.dev> <8f23848b8ac657b4b4a2da04da242039c59e9ad9826a8d5fa0f5aee55acfecc9@mail.kernel.org> <87a4zdepdh.fsf@linux.dev> Date: Sat, 20 Dec 2025 10:43:06 -0800 Message-ID: <87zf7d6ll1.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 4DE56A000F X-Rspamd-Server: rspam03 X-Stat-Signature: 56gxo9r4j41ckpbatk8u5y4ibcfttqir X-Rspam-User: X-HE-Tag: 1766256200-70531 X-HE-Meta: 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 UDD/L3tN Yr8PktOtMkl8rc7KeQvZCQtdItMS8z5lBSUvM81P/H30hX+Yfi7jnttBFRBoIHDeu4xZHBni8g2Mtcw7vGBIsrAT+RafD0jcPMxCfxgVuY7nY1pxTO/03qzW9RucXShz1mUfIQYdbWbNewBmfDFUxmybdk/jVRThIhN79cXGazJ26z6A9IGaQDFVgvYhEp14CBGNp9r3lP8Sv45WY1f4yCy4KZ/mEmmLvOYqHeVvD9wbqplGqIJukUL28LYjf/asZQv8BIDvCU0ZpZWIkNHnr1+zBX5sGDlKWIpVNCdJpEG5nLs9G9wcNzqbnyKbBAgz6QiO0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Chris Mason writes: > On 12/19/25 11:41 PM, Roman Gushchin wrote: >> bot+bpf-ci@kernel.org writes: >> >>>> diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c >>>> index d84fe6f3ed43..858eb43766ce 100644 >>>> --- a/mm/bpf_memcontrol.c >>>> +++ b/mm/bpf_memcontrol.c >>>> @@ -103,6 +103,22 @@ __bpf_kfunc unsigned long bpf_mem_cgroup_usage(struct mem_cgroup *memcg) >>>> return mem_cgroup_usage(memcg, false) * PAGE_SIZE; >>>> } >>>> >>>> +/** >>>> + * bpf_mem_cgroup_memory_events - Read memory cgroup's memory event value >>>> + * @memcg: memory cgroup >>>> + * @event: memory event id >>>> + * >>>> + * Returns current memory event count. >>>> + */ >>>> +__bpf_kfunc unsigned long bpf_mem_cgroup_memory_events(struct mem_cgroup *memcg, >>>> + enum memcg_memory_event event) >>>> +{ >>>> + if (event >= MEMCG_NR_MEMORY_EVENTS) >>>> + return (unsigned long)-1; >>> >>> Should this also check for negative values? The enum type is typically >>> signed, so a BPF program passing a negative event value would pass this >>> check but cause an out-of-bounds read from memcg->memory_events[]. >>> >>> The similar bpf_mem_cgroup_page_state() in this same file uses: >>> >>> if (idx < 0 || idx >= MEMCG_NR_STAT) >>> >>> which checks both bounds. Could the check here be changed to: >>> >>> if (event < 0 || event >= MEMCG_NR_MEMORY_EVENTS) >>> >>> to match that pattern? >> >> No, the bpf verifier enforces event > 0. >> It's a false positive. > > I'll add some words here to the bpf prompts, thanks Roman. I'll try to play with it too, hopefully we can fix it. Thanks!