From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta1.migadu.com (out-188.mta1.migadu.com [95.215.58.188]) (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 25076134B1 for ; Wed, 24 Jul 2024 02:24:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721787870; cv=none; b=G3DTSMIjY9Cpb9nKxlr1curBF7GcIqqjD+rTbCJmXc5PH/rIrkaVyQau+7nqSoMO+cwZzy4nTdAPhc1TQRU1pPIDFZsSkfB9zrwSVDy+Uu+d7GSuN0Ipm2Q5inggy/dl0QMl2mTxLUkTGf97Tn9r+Q3rRv3YxtNad4fMleuwXkM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721787870; c=relaxed/simple; bh=BvGsXL/JgX6GUqmfolhYf92QKVOLf/UNa/GGiX9WbJs=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=F3tKhTsurr4j7pL0LReqs6huIyqiktbKCogMOXFmnaBfM+gKehzqIm7GtsKiY56eL+87dgzgmFdqmC8xzisBfaB2ycDRPV4STlBwtuu5QRKKp829K4fhLuV/tx2lCwLaGHloIj0dNOI/svCzy/wNTg3o5fvRPTBVJNk4PJdCSPY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=ALgziQ//; arc=none smtp.client-ip=95.215.58.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="ALgziQ//" Content-Type: text/plain; charset=us-ascii DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1721787866; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EpolYlv0Jnv1Ymoo+FfzdPp8dy1j/5y+7C6zCgpN3ac=; b=ALgziQ//EGixEzlmfUfTyzaAIpYyVX0IwvtL6gVujv50Ji/oypOgovc4ddjnCrf5LatyGW zbTbzlz7FrsxNqFXal5qeimKflmVYnqxvKo8BTjvX+zepZev4qJ6ICnvWDfQAMAggTxyA0 B29MieaNH1cWGXJqgJa0iVe84tgmrZg= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3774.600.62\)) Subject: Re: [PATCH] mm: list_lru: fix UAF for memory cgroup X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: <20240723174540.18992614c476d77e7d9fb1e6@linux-foundation.org> Date: Wed, 24 Jul 2024 10:23:43 +0800 Cc: Muchun Song , Johannes Weiner , Nhat Pham , Linux Memory Management List , LKML Content-Transfer-Encoding: quoted-printable Message-Id: <62BBC2A6-D6C3-48B8-B049-932E3BC16F31@linux.dev> References: <20240718083607.42068-1-songmuchun@bytedance.com> <20240723174540.18992614c476d77e7d9fb1e6@linux-foundation.org> To: Andrew Morton X-Migadu-Flow: FLOW_OUT > On Jul 24, 2024, at 08:45, Andrew Morton = wrote: >=20 > On Thu, 18 Jul 2024 16:36:07 +0800 Muchun Song = wrote: >=20 >> The mem_cgroup_from_slab_obj() is supposed to be called under rcu >> lock or cgroup_mutex or others which could prevent returned memcg >> from being freed. Fix it by adding missing rcu read lock. >=20 > "or others" is rather vague. What others? Like objcg_lock. I have added this one into obj_cgroup_memcg(). >=20 >> @@ -109,14 +110,20 @@ EXPORT_SYMBOL_GPL(list_lru_add); >>=20 >> bool list_lru_add_obj(struct list_lru *lru, struct list_head *item) >> { >> + bool ret; >> int nid =3D page_to_nid(virt_to_page(item)); >> - struct mem_cgroup *memcg =3D list_lru_memcg_aware(lru) ? >> - mem_cgroup_from_slab_obj(item) : NULL; >> + struct mem_cgroup *memcg; >>=20 >> - return list_lru_add(lru, item, nid, memcg); >> + rcu_read_lock(); >> + memcg =3D list_lru_memcg_aware(lru) ? = mem_cgroup_from_slab_obj(item) : NULL; >> + ret =3D list_lru_add(lru, item, nid, memcg); >> + rcu_read_unlock(); >=20 > We don't need rcu_read_lock() to evaluate NULL. >=20 > memcg =3D NULL; > if (list_lru_memcg_aware(lru)) { > rcu_read_lock(); > memcg =3D mem_cgroup_from_slab_obj(item); > rcu_read_unlock(); Actually, the access to memcg is in list_lru_add(), so the rcu lock = should also cover this function rather than only mem_cgroup_from_slab_obj(). Something like: memcg =3D NULL; if (list_lru_memcg_aware(lru)) { rcu_read_lock(); memcg =3D mem_cgroup_from_slab_obj(item); } ret =3D list_lru_add(lru, item, nid, memcg); if (list_lru_memcg_aware(lru)) rcu_read_unlock(); Not concise. I don't know if this is good. > } >=20 > Seems worthwhile? >=20 >=20