linux-kernel - Re: [PATCH v3 0/4] Add overflow checks for several syscalls

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Date:   Mon, 6 Feb 2023 08:52:09 +0800
From:   mawupeng <mawupeng1@...wei.com>
To:     <david@...hat.com>, <akpm@...ux-foundation.org>
CC:     <mawupeng1@...wei.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <kuleshovmail@...il.com>,
        <aneesh.kumar@...ux.ibm.com>
Subject: Re: [PATCH v3 0/4] Add overflow checks for several syscalls



On 2023/2/4 1:10, David Hildenbrand wrote:
> On 28.01.23 07:32, Wupeng Ma wrote:
>> From: Ma Wupeng <mawupeng1@...wei.com>
>>
>> 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.
>>
>> Similar logic is used to fix problems with multiple syscalls.
>>
>> Changelog since v2[2]:
>> - modified the way of checking overflows based on Andrew's comments
>>
>> Changelog since v1[1]:
>> - only check overflow rather than access_ok to keep backward-compatibility
> 
> Do you have some test cases and could we add them to LTP, for example?

The basic idea is setting param len to ULONG_MAX. while will overflow if PAGE_ALIGN(len).

Here are some simple examples:

mlock(addr, ULONG_MAX);
set_mempolicy_home_node(addr, ULONG_MAX, 0, 0);
mbind(addr, ULONG_MAX, MPOL_BIND, &nodemask, max_node, MPOL_MF_MOVE_ALL);
msync(addr, ULONG_MAX, MS_ASYNC);

>