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Fri, 7 Aug 2020 12:49:56 +0000 (UTC) Received: from localhost (ovpn-12-31.pek2.redhat.com [10.72.12.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 547355DA33; Fri, 7 Aug 2020 12:49:54 +0000 (UTC) Date: Fri, 7 Aug 2020 20:49:51 +0800 From: Baoquan He To: Wei Yang Cc: mike.kravetz@oracle.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 02/10] mm/hugetlb: make sure to get NULL when list is empty Message-ID: <20200807124951.GM14854@MiWiFi-R3L-srv> References: <20200807091251.12129-1-richard.weiyang@linux.alibaba.com> <20200807091251.12129-3-richard.weiyang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200807091251.12129-3-richard.weiyang@linux.alibaba.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Rspamd-Queue-Id: DAAA0180442C2 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 08/07/20 at 05:12pm, Wei Yang wrote: > list_first_entry() may not return NULL even when the list is empty. > > Let's make sure the behavior by using list_first_entry_or_null(), > otherwise it would corrupt the list. > > Signed-off-by: Wei Yang > --- > mm/hugetlb.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 62ec74f6d03f..0a2f3851b828 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -237,7 +237,8 @@ get_file_region_entry_from_cache(struct resv_map *resv, long from, long to) > VM_BUG_ON(resv->region_cache_count <= 0); We have had above line, is it possible to be NULL from list_first_entry? > > resv->region_cache_count--; > - nrg = list_first_entry(&resv->region_cache, struct file_region, link); > + nrg = list_first_entry_or_null(&resv->region_cache, > + struct file_region, link); > VM_BUG_ON(!nrg); > list_del(&nrg->link); > > -- > 2.20.1 (Apple Git-117) > >