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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 17 Jun 2019 07:46:58 +0100 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5H6kvaZ37486936 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 17 Jun 2019 06:46:57 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 869A5A405B; Mon, 17 Jun 2019 06:46:57 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ED690A4064; Mon, 17 Jun 2019 06:46:55 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.8.53]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 17 Jun 2019 06:46:55 +0000 (GMT) Date: Mon, 17 Jun 2019 09:46:54 +0300 From: Mike Rapoport To: "Alastair D'Silva" Cc: alastair@d-silva.org, Andrew Morton , David Hildenbrand , Oscar Salvador , Michal Hocko , Pavel Tatashin , Wei Yang , Qian Cai , Thomas Gleixner , Ingo Molnar , Josh Poimboeuf , Peter Zijlstra , Konrad Rzeszutek Wilk , Jiri Kosina , Mukesh Ojha , Arun KS , Mike Rapoport , Baoquan He , Logan Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/5] mm: Trigger bug on if a section is not found in __section_nr References: <20190617043635.13201-1-alastair@au1.ibm.com> <20190617043635.13201-2-alastair@au1.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190617043635.13201-2-alastair@au1.ibm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19061706-0020-0000-0000-0000034AB4D6 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19061706-0021-0000-0000-0000219DF855 Message-Id: <20190617064653.GA16810@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-17_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906170062 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: On Mon, Jun 17, 2019 at 02:36:27PM +1000, Alastair D'Silva wrote: > From: Alastair D'Silva > > If a memory section comes in where the physical address is greater than > that which is managed by the kernel, this function would not trigger the > bug and instead return a bogus section number. > > This patch tracks whether the section was actually found, and triggers the > bug if not. > > Signed-off-by: Alastair D'Silva > --- > mm/sparse.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index fd13166949b5..104a79fedd00 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -105,20 +105,23 @@ static inline int sparse_index_init(unsigned long section_nr, int nid) > int __section_nr(struct mem_section* ms) > { > unsigned long root_nr; > - struct mem_section *root = NULL; > + struct mem_section *found = NULL; > + struct mem_section *root; > > for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) { > root = __nr_to_section(root_nr * SECTIONS_PER_ROOT); > if (!root) > continue; > > - if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT))) > - break; > + if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT))) { > + found = root; > + break; > + } > } > > - VM_BUG_ON(!root); > + VM_BUG_ON(!found); Isn't it enough to check for root_nr == NR_SECTION_ROOTS? > > - return (root_nr * SECTIONS_PER_ROOT) + (ms - root); > + return (root_nr * SECTIONS_PER_ROOT) + (ms - found); It'll still return a bogus section number with CONFIG_DEBUG_VM=n > } > #else > int __section_nr(struct mem_section* ms) > -- > 2.21.0 > -- Sincerely yours, Mike.