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[2003:cb:c706:7900:b84d:7f2e:b638:3092]) by smtp.gmail.com with ESMTPSA id k6-20020adfb346000000b0027cb20605e3sm2470036wrd.105.2023.02.03.09.14.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Feb 2023 09:14:30 -0800 (PST) Message-ID: <753c53d3-84a6-da73-4121-0db4a71e4fde@redhat.com> Date: Fri, 3 Feb 2023 18:14:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH v3 1/4] mm/mlock: return EINVAL if len overflows for mlock/munlock Content-Language: en-US To: Wupeng Ma , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kuleshovmail@gmail.com, aneesh.kumar@linux.ibm.com References: <20230128063229.989058-1-mawupeng1@huawei.com> <20230128063229.989058-2-mawupeng1@huawei.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230128063229.989058-2-mawupeng1@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28.01.23 07:32, 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. > > Return 0 early to avoid burn a bunch of cpu cycles if len == 0. > > Signed-off-by: Ma Wupeng > --- > mm/mlock.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/mm/mlock.c b/mm/mlock.c > index 7032f6dd0ce1..eb09968ba27f 100644 > --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -478,8 +478,6 @@ static int apply_vma_lock_flags(unsigned long start, size_t len, > end = start + len; > if (end < start) > return -EINVAL; > - if (end == start) > - return 0; > vma = mas_walk(&mas); > if (!vma) > return -ENOMEM; > @@ -575,7 +573,13 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla > if (!can_do_mlock()) > return -EPERM; > > + if (!len) > + return 0; > + > len = PAGE_ALIGN(len + (offset_in_page(start))); > + if (!len) > + return -EINVAL; > + > start &= PAGE_MASK; The "ordinary" overflows are detected in apply_vma_lock_flags(), correct? -- Thanks, David / dhildenb