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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 CC: , , , , Subject: Re: [PATCH v4 1/4] mm/mlock: return EINVAL if len overflows for mlock/munlock Content-Language: en-US To: , References: <20230320024739.224850-1-mawupeng1@huawei.com> <20230320024739.224850-2-mawupeng1@huawei.com> <27b9cb5b-0118-f989-80c2-6a143a4232af@redhat.com> <3ef9520c-6713-527a-0214-ac7a8bb2d49c@huawei.com> <6dd844f7-d43b-c744-f295-9f14c68d3928@redhat.com> <8be13253-b4ca-b134-3e85-b4097484bb29@huawei.com> <9583bc53-716d-f2ff-38e7-1dda7e57dd5d@redhat.com> <9b531543-9f97-178f-8a97-494322410806@redhat.com> From: mawupeng In-Reply-To: <9b531543-9f97-178f-8a97-494322410806@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.120] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 97C67C0017 X-Stat-Signature: whbniwqudyzaezwossyasqug7aipmrqh X-HE-Tag: 1679476853-276263 X-HE-Meta: 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 NAvgoWS6 qpmgRJdCL3+VT/CutrA+9MjnIZig0O7PFCJ4tt3bkRsL8ojU0E+WMsxWopebGkFKP3RZOvfN8zPZWA3vFNm356NGgO6VyTM5euLbNuvIwXUlxuuFYguJHEWGlbcFejwDBrD2QgraLZca83oLsETfL+BhAnYOE/XlGNsF8Nl31F4l+OCI= 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 2023/3/22 17:01, David Hildenbrand wrote: > On 22.03.23 09:54, David Hildenbrand wrote: >> On 22.03.23 03:14, mawupeng wrote: >>> >>> >>> On 2023/3/21 22:19, David Hildenbrand wrote: >>>> On 21.03.23 08:44, mawupeng wrote: >>>>> >>>>> >>>>> On 2023/3/20 18:54, David Hildenbrand wrote: >>>>>> On 20.03.23 03:47, Wupeng Ma wrote: >>>>>>> From: Ma Wupeng >>>>>>> >>>>>>> While testing mlock, we have a problem if the len of mlock is ULONG_MAX. >>>>>>> The return value of mlock is zero. But nothing will be locked since the >>>>>>> len in do_mlock overflows to zero due to the following code in mlock: >>>>>>> >>>>>>>       len = PAGE_ALIGN(len + (offset_in_page(start))); >>>>>>> >>>>>>> The same problem happens in munlock. >>>>>>> >>>>>>> Add new check and return -EINVAL to fix this overflowing scenarios since >>>>>>> they are absolutely wrong. >>>>>> >>>>>> Thinking again, wouldn't we reject mlock(0, ULONG_MAX) now as well? >>>>> >>>>> mlock will return 0 if len is zero which is the same w/o this patchset. >>>>> Here is the calltrace if len is zero. >>>>> >>>>> mlock(len == 0) >>>>>       do_mlock(len == 0) >>>>>           if (!len) >>>>>               return 0 >>>>> >>>> >>>> I was asking about addr=0, len=ULONG_MAX. >>>> >>>> IIUC, that used to work but could now fail? I haven't played with it, though. >>> >>> Thanks for reviewing. >>> >>> Previous for add = 0 and len == ULONG_MAX, mlock will return ok(0) since len overflows to zero. >>> IFAICT, this is not right since mlock do noting(lock nothing) and return ok(0). >>> >>> With this patch, for the same situation, mlock can return EINVAL as expected. >> >> Quoting the man page: >> >> "EINVAL (mlock(),  mlock2(),  and  munlock()) The result of the addition >> addr+len was less than addr (e.g., the addition may have resulted in an >> overflow)." >> >> ULONG_MAX+0 = ULONG_MAX >> >> There is no overflow expected. The proper way to implement it would be >> to handle that case and not fail with EINVAL. >> >> At least that would be expected when reading the man page. >> > > As a side note, I agree that failing with EINVAL is better than doing noting (mlocking nothing). But I am not sure what we are expected to do in that case ... the man page is a bit vague on that. Thanks for you reviewing. Can we try to expand the man page since overflow is considered in man page? >