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c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Wq4bW80PYQOUvc+r7HK1lpXC6FPGn4j7cEEATFFs/9U=; b=Mx0EAq/g16hSUXMAcEp73/k85Z8rbHTKX/Aj1YuQyWAyXQRT9Q0BferCX8iVzyQWAM K52OL0pG3zt38cnIE6PsqHuGong5ebsRypAGKETjM6RCfA1shJs7wgBsWwFv0zBITp1H c8bN9Bcz4hFvP+t/0JPKF9eTvSk2wwT6XEB3pnAI8ynHP7Q+CA9EVoMsFSNwnr58Ibx5 wv2LTskqztJidcl31CTt0jtw5Qtj2bXHS0bJPcGB5EceiyAYri3vEErplKwL1zGjwB+Z C/oLRUwIPASpw4hJYLElfMhEM6kNLr0EFLYctO4bIUsMv6GcqpagP1W79m/gm0ZkSPho MNyw== X-Gm-Message-State: AOAM531BsTL93trWZDpzrV9nsyb6EmhRWx5RmE7bnTgCHLS8qiavoMCh p4xe6EGh6vSQ/T1LR7+OmEhCUyy0jB5VI9Eyh0Fu7g== X-Google-Smtp-Source: ABdhPJxJQPdfEzCXFS9OWhsPamjtFq0jc35saCUnIZCNBxX9HEpqYBDHd3D3HTIPSLCWBE7TfpMBNcTzLVi0eqdnFrc= X-Received: by 2002:a17:902:221:: with SMTP id 30mr19150363plc.222.1598582056522; Thu, 27 Aug 2020 19:34:16 -0700 (PDT) MIME-Version: 1.0 References: <20200822095328.61306-1-songmuchun@bytedance.com> <20200824135924.b485e000d358cee817c4f05c@linux-foundation.org> <79800508-54c9-4cda-02de-29b1a6912e75@oracle.com> <231ec1f1-fe7a-c48a-2427-1311360d4b9b@oracle.com> In-Reply-To: From: Muchun Song Date: Fri, 28 Aug 2020 10:33:40 +0800 Message-ID: Subject: Re: [External] Re: [PATCH] mm/hugetlb: Fix a race between hugetlb sysctl handlers To: Mike Kravetz Cc: Andrew Morton , Andi Kleen , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 98D5B1004EF72 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 Fri, Aug 28, 2020 at 5:51 AM Mike Kravetz wrote: > > On 8/25/20 7:47 PM, Muchun Song wrote: > > > > CPU0: CPU1: > > proc_sys_write > > hugetlb_sysctl_handler proc_sys_call_handler > > hugetlb_sysctl_handler_common hugetlb_sysctl_handler > > table->data = &tmp; hugetlb_sysctl_handler_common > > table->data = &tmp; > > proc_doulongvec_minmax > > do_proc_doulongvec_minmax sysctl_head_finish > > __do_proc_doulongvec_minmax > > i = table->data; > > *i = val; // corrupt CPU1 stack > > Thanks Muchun! > Can you please add this to the commit message. OK, I will do that. Thanks. > > Also, when looking closer at the patch I do not think setting table->maxlen > is necessary in these routines. maxlen is set when the hugetlb ctl_table > entries are defined and initialized. This is not something you introduced. > The unnecessary assignments are in the existing code. However, there is no > need to carry them forward. Yeah, I agree with you. I will remove the unnecessary assignment of table->maxlen. > > -- > Mike Kravetz -- Yours, Muchun