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]) by smtp.lore.kernel.org (Postfix) with ESMTP id B010CC3DA4A for ; Mon, 19 Aug 2024 10:02:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 26BA36B0085; Mon, 19 Aug 2024 06:02:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 21B806B0088; Mon, 19 Aug 2024 06:02:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0E2FD6B008A; Mon, 19 Aug 2024 06:02:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id E8B876B0085 for ; Mon, 19 Aug 2024 06:02:46 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 92A651A111E for ; Mon, 19 Aug 2024 10:02:46 +0000 (UTC) X-FDA: 82468555932.15.154A2A0 Received: from mail-ua1-f43.google.com (mail-ua1-f43.google.com [209.85.222.43]) by imf16.hostedemail.com (Postfix) with ESMTP id C779A180022 for ; Mon, 19 Aug 2024 10:02:44 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=RY6g++aV; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf16.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.222.43 as permitted sender) smtp.mailfrom=21cnbao@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724061702; a=rsa-sha256; cv=none; b=tVm1PhBnkX7cIR42JqmFxodxuMqVdUUHnDTn2ojaze8sTeI7MDAxRXvqcngeMatCRXMPBL zBcBdTLemIFHzVCDGRpRztCoctWathnlf68viAbz3QXLBzKWxAGucbw67wiNs9d04u46AT J9jtATGg0QIQsVjctA9rsCrUS4x6SC4= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=RY6g++aV; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf16.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.222.43 as permitted sender) smtp.mailfrom=21cnbao@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724061702; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=d62lfnArQ+W+wXiW8uVMEV5IRAsxo/eNQMcf2FOMm2M=; b=0JfOIZ45ZPpZmb9a0xZjb5u6/TjJGEid+ebBm5YeHMo2SfqgvgNIXgDIlyh0NAALejQ5pR PuUcjutwkhffWQQNiAujiSAQSORP9V5GJ+yLByts3Zs1lWVT5kGYHHMlrqyl7/l2SjGGrC 52vqYiF5+ZwRLKvFs7Lzb2I/Fi54s9c= Received: by mail-ua1-f43.google.com with SMTP id a1e0cc1a2514c-81f91171316so2580130241.0 for ; Mon, 19 Aug 2024 03:02:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1724061764; x=1724666564; darn=kvack.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=d62lfnArQ+W+wXiW8uVMEV5IRAsxo/eNQMcf2FOMm2M=; b=RY6g++aVXgnJxqZAa6PHxcQJgEbrs/HM9LEwEXjFl3vukNQv+eMfTdceZ6dAErpn/v Ydhco63czv4JR1OTi30hy0lhrVrRE/tVvY/t8/0KfYGYKVm6eFGIqBYK3s5EY45SN3mQ BrBxDc7z/unqfOMeHU8JDungN3sSyOhVmIqH4PJdwTqUiq+2+a6YFgruLiTeVZhNzM/t YfkTODtbaqkYDzkg5oxb68LptcenS6z3ku2t7+kIEEzN9+IQ2g6BEkkGq5Dl8YOiQrxG qCxYPAmQ+YnwGdjlzG6DXJXS1IkT2r3Ct6BMFklec/wmZ2KJRAwY+dDClSTcfBSq6Ku1 LT+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1724061764; x=1724666564; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=d62lfnArQ+W+wXiW8uVMEV5IRAsxo/eNQMcf2FOMm2M=; b=n103nuFiZ81T2RjcU7w2ae9ijswRuwlyRTuv5AGWSt7Q1xKRdMdZD85B74QnpkiKMB x+OATDNnD4o4McX6YtwbGrawjgrjAIvouQpjlhkQzD5D0AWyCQmd5nHOWUXNRLUETeK7 tFILU73/Uo6FNrEsrgYbbFinKyQpa/NbGZnoOq5s4ErD5/l8m3bqsJuEYlAoo7Yf42na PGJa7mOQQ1duKPZW4JMjsdgF7AQc6IhQs5Kb4wDguYQr1/Hwpj9fjG8legLJdYQTA/1B ltvcwoz50JMfvMs+3K1cv4r5SuLZ4aJ66ApxewANU3BaxlD8Hs03HRY8XO/cVKcpIfBy BxXQ== X-Forwarded-Encrypted: i=1; AJvYcCUqZOHKEyyvBCTvHKjD217ZUZdxFcwdcVVslH+Xb9i+Hmc9vX4U7AQ0M0qllHrlUZVHHhpKVIwDve50hy+ac8tJ5+g= X-Gm-Message-State: AOJu0YznBaECBGDxo5ehjrTmfwg62XziMLyFvi89V3kpwcsMiL9EqtUj SSr2fPqoLH+5ajYtthk0XyFRakpZThPoCooCylUWaWaJ1SK6xCg/qV3FD7C93Q61Qt7e8RYtI+0 fbRTdlwO5+VHRuoY5HzLZSI0GtsI= X-Google-Smtp-Source: AGHT+IE6NFzpaEfiuWE5jrWWKZxObh1oplK9M250rQQ6GDhiDdlVvYZCeY8C06spkAjH/fxZutvKMRNbtztrJdi43OI= X-Received: by 2002:a05:6122:29c8:b0:4f5:2adf:3445 with SMTP id 71dfb90a1353d-4fc591623e7mr7224555e0c.7.1724061763685; Mon, 19 Aug 2024 03:02:43 -0700 (PDT) MIME-Version: 1.0 References: <20240817062449.21164-1-21cnbao@gmail.com> <20240817062449.21164-4-21cnbao@gmail.com> <5654b71c-1d9d-4c48-b28b-664662da8897@redhat.com> <416ac265-ced2-4f90-a347-0a256edf7fdf@redhat.com> In-Reply-To: <416ac265-ced2-4f90-a347-0a256edf7fdf@redhat.com> From: Barry Song <21cnbao@gmail.com> Date: Mon, 19 Aug 2024 22:02:32 +1200 Message-ID: Subject: Re: [PATCH v3 3/4] mm: BUG_ON to avoid NULL deference while __GFP_NOFAIL fails To: David Hildenbrand Cc: akpm@linux-foundation.org, linux-mm@kvack.org, 42.hyeyoo@gmail.com, cl@linux.com, hailong.liu@oppo.com, hch@infradead.org, iamjoonsoo.kim@lge.com, mhocko@suse.com, penberg@kernel.org, rientjes@google.com, roman.gushchin@linux.dev, torvalds@linux-foundation.org, urezki@gmail.com, v-songbaohua@oppo.com, vbabka@suse.cz, virtualization@lists.linux.dev, Christoph Hellwig , Lorenzo Stoakes , Kees Cook , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Jason Wang , Maxime Coquelin , "Michael S. Tsirkin" , Xuan Zhuo Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C779A180022 X-Stat-Signature: 4trj5hsyb58z38914sics6hy36smr6eq X-Rspam-User: X-HE-Tag: 1724061764-173110 X-HE-Meta: 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 QcW9aFq5 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 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: On Mon, Aug 19, 2024 at 9:55=E2=80=AFPM David Hildenbrand wrote: > > On 19.08.24 11:47, Barry Song wrote: > > On Mon, Aug 19, 2024 at 9:43=E2=80=AFPM David Hildenbrand wrote: > >> > >> On 17.08.24 08:24, Barry Song wrote: > >>> From: Barry Song > >>> > >>> We have cases we still fail though callers might have __GFP_NOFAIL. = Since > >>> they don't check the return, we are exposed to the security risks for= NULL > >>> deference. > >>> > >>> Though BUG_ON() is not encouraged by Linus, this is an unrecoverable > >>> situation. > >>> > >>> Christoph Hellwig: > >>> The whole freaking point of __GFP_NOFAIL is that callers don't handle > >>> allocation failures. So in fact a straight BUG is the right thing > >>> here. > >>> > >>> Vlastimil Babka: > >>> It's just not a recoverable situation (WARN_ON is for recoverable > >>> situations). The caller cannot handle allocation failure and at the s= ame > >>> time asked for an impossible allocation. BUG_ON() is a guaranteed oop= s > >>> with stracktrace etc. We don't need to hope for the later NULL pointe= r > >>> dereference (which might if really unlucky happen from a different > >>> context where it's no longer obvious what lead to the allocation fail= ing). > >>> > >>> Michal Hocko: > >>> Linus tends to be against adding new BUG() calls unless the failure i= s > >>> absolutely unrecoverable (e.g. corrupted data structures etc.). I am > >>> not sure how he would look at simply incorrect memory allocator usage= to > >>> blow up the kernel. Now the argument could be made that those failure= s > >>> could cause subtle memory corruptions or even be exploitable which mi= ght > >>> be a sufficient reason to stop them early. > >>> > >>> Signed-off-by: Barry Song > >>> Reviewed-by: Christoph Hellwig > >>> Acked-by: Vlastimil Babka > >>> Acked-by: Michal Hocko > >>> Cc: Uladzislau Rezki (Sony) > >>> Cc: Lorenzo Stoakes > >>> Cc: Christoph Lameter > >>> Cc: Pekka Enberg > >>> Cc: David Rientjes > >>> Cc: Joonsoo Kim > >>> Cc: Roman Gushchin > >>> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> > >>> Cc: Linus Torvalds > >>> Cc: Kees Cook > >>> Cc: "Eugenio P=C3=A9rez" > >>> Cc: Hailong.Liu > >>> Cc: Jason Wang > >>> Cc: Maxime Coquelin > >>> Cc: "Michael S. Tsirkin" > >>> Cc: Xuan Zhuo > >>> --- > >>> include/linux/slab.h | 4 +++- > >>> mm/page_alloc.c | 4 +++- > >>> mm/util.c | 1 + > >>> 3 files changed, 7 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/include/linux/slab.h b/include/linux/slab.h > >>> index c9cb42203183..4a4d1fdc2afe 100644 > >>> --- a/include/linux/slab.h > >>> +++ b/include/linux/slab.h > >>> @@ -827,8 +827,10 @@ kvmalloc_array_node_noprof(size_t n, size_t size= , gfp_t flags, int node) > >>> { > >>> size_t bytes; > >>> > >>> - if (unlikely(check_mul_overflow(n, size, &bytes))) > >>> + if (unlikely(check_mul_overflow(n, size, &bytes))) { > >>> + BUG_ON(flags & __GFP_NOFAIL); > >>> return NULL; > >>> + } > >>> > >>> return kvmalloc_node_noprof(bytes, flags, node); > >>> } > >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c > >>> index 60742d057b05..d2c37f8f8d09 100644 > >>> --- a/mm/page_alloc.c > >>> +++ b/mm/page_alloc.c > >>> @@ -4668,8 +4668,10 @@ struct page *__alloc_pages_noprof(gfp_t gfp, u= nsigned int order, > >>> * There are several places where we assume that the order val= ue is sane > >>> * so bail out early if the request is out of bound. > >>> */ > >>> - if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)) > >>> + if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)) { > >>> + BUG_ON(gfp & __GFP_NOFAIL); > >>> return NULL; > >>> + } > >>> > >>> gfp &=3D gfp_allowed_mask; > >>> /* > >>> diff --git a/mm/util.c b/mm/util.c > >>> index ac01925a4179..678c647b778f 100644 > >>> --- a/mm/util.c > >>> +++ b/mm/util.c > >>> @@ -667,6 +667,7 @@ void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(s= ize, b), gfp_t flags, int node) > >>> > >>> /* Don't even allow crazy sizes */ > >>> if (unlikely(size > INT_MAX)) { > >>> + BUG_ON(flags & __GFP_NOFAIL); > >> > >> No new BUG_ON please. WARN_ON_ONCE() + recovery code might be suitable= here. > > > > Hi David, > > WARN_ON_ONCE() might be fine but I don't see how it is possible to rec= over. > > Just return NULL? "shit in shit out" :) ? Returning NULL is perfectly right if gfp doesn't include __GFP_NOFAIL, as it's the caller's responsibility to check the return value. However, wit= h __GFP_NOFAIL, users will directly dereference *(p + offset) even when p =3D=3D NULL. It is how __GFP_NOFAIL is supposed to work. > > -- > Cheers, > > David / dhildenb >