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[45.249.212.190]) by mx.google.com with ESMTPS id t14si6829245vsp.341.2019.04.09.21.21.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Apr 2019 21:21:08 -0700 (PDT) Received-SPF: pass (google.com: domain of yuyufen@huawei.com designates 45.249.212.190 as permitted sender) client-ip=45.249.212.190; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yuyufen@huawei.com designates 45.249.212.190 as permitted sender) smtp.mailfrom=yuyufen@huawei.com Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id C31E9789D2AF0F397F06; Wed, 10 Apr 2019 12:21:00 +0800 (CST) Received: from [127.0.0.1] (10.177.219.49) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.408.0; Wed, 10 Apr 2019 12:20:51 +0800 Subject: Re: [PATCH] hugetlbfs: fix protential null pointer dereference To: Mike Kravetz , CC: , , , References: <20190410025037.144872-1-yuyufen@huawei.com> From: yuyufen Message-ID: <1a43c780-3ded-a7bc-391e-f85295eb942d@huawei.com> Date: Wed, 10 Apr 2019 12:20:50 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.177.219.49] X-CFilter-Loop: Reflected 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: Hi, Mike On 2019/4/10 11:38, Mike Kravetz wrote: > On 4/9/19 7:50 PM, Yufen Yu wrote: >> After commit 58b6e5e8f1ad ("hugetlbfs: fix memory leak for resv_map"), >> i_mapping->private_data will be NULL for mode that is not regular and link. >> Then, it might cause NULL pointer derefernce in hugetlb_reserve_pages() >> when do_mmap. We can avoid protential null pointer dereference by >> judging whether it have been allocated. >> >> Fixes: 58b6e5e8f1ad ("hugetlbfs: fix memory leak for resv_map") >> Cc: Kirill A. Shutemov >> Cc: Naoya Horiguchi >> Cc: Michal Hocko >> Signed-off-by: Yufen Yu > Thanks for catching this. I mistakenly thought all the code was checking > for NULL resv_map. That certainly is one (and only) place where it is not > checked. Have you verified that this is possible? Should be pretty easy > to do. If you have not, I can try to verify tomorrow. I honestly say that I don't have verified. >> --- >> mm/hugetlb.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index 97b1e0290c66..15e4baf2aa7d 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -4465,6 +4465,8 @@ int hugetlb_reserve_pages(struct inode *inode, >> */ >> if (!vma || vma->vm_flags & VM_MAYSHARE) { >> resv_map = inode_resv_map(inode); >> + if (!resv_map) >> + return -EOPNOTSUPP; > I'm not sure about the return code here. Note that all callers of > hugetlb_reserve_pages() force return value of -ENOMEM if non-zero value > is returned. I think we would like to return -EACCES in this situation. > The mmap man page says: > > EACCES A file descriptor refers to a non-regular file. Or ... Thanks for your suggestion. It is more reasonable to use -EACCES. Yufen Thanks.