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[2003:cb:c704:6200:8129:46d3:fa82:23f8]) by smtp.gmail.com with ESMTPSA id p12-20020a5d48cc000000b00241fab5a296sm9152844wrs.40.2023.02.06.09.05.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Feb 2023 09:05:02 -0800 (PST) Message-ID: <10a3929a-7109-169f-6e42-e51c83305567@redhat.com> Date: Mon, 6 Feb 2023 18:05:01 +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: mawupeng , 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> <753c53d3-84a6-da73-4121-0db4a71e4fde@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06.02.23 01:48, mawupeng wrote: > > > On 2023/2/4 1:14, David Hildenbrand wrote: >> 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? > > Overflow is not checked anywhere however the ordinary return early if len == 0 is detected in apply_vma_lock_flags(). > I meant the end = start + len; if (end < start) return -EINVAL; Essentially, what I wanted to double-check is that with your changes, we catch all kinds of overflows as documented in the man page, correct? -- Thanks, David / dhildenb