From: Yisheng Xie <xieyisheng1@huawei.com>
To: Vlastimil Babka <vbabka@suse.cz>,
akpm@linux-foundation.org, mhocko@suse.com, mingo@kernel.org,
rientjes@google.com, n-horiguchi@ah.jp.nec.com,
salls@cs.ucsb.edu
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
tanxiaojun@huawei.com, linux-api@vger.kernel.org
Subject: Re: [PATCH RFC v2 3/4] mm/mempolicy: fix the check of nodemask from user
Date: Tue, 31 Oct 2017 19:01:06 +0800 [thread overview]
Message-ID: <65c0e6cb-28b4-f202-1d7f-278b5dfc3440@huawei.com> (raw)
In-Reply-To: <56c4cdbf-c228-6203-285c-15f19a841538@suse.cz>
On 2017/10/31 17:30, Vlastimil Babka wrote:
> On 10/27/2017 12:14 PM, Yisheng Xie wrote:
>> + /*
>> + * When the user specified more nodes than supported just check
>> + * if the non supported part is all zero.
>> + *
>> + * If maxnode have more longs than MAX_NUMNODES, check
>> + * the bits in that area first. And then go through to
>> + * check the rest bits which equal or bigger than MAX_NUMNODES.
>> + * Otherwise, just check bits [MAX_NUMNODES, maxnode).
>> + */
>> if (nlongs > BITS_TO_LONGS(MAX_NUMNODES)) {
>> for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) {
>> - unsigned long t;
>> if (get_user(t, nmask + k))
>> return -EFAULT;
>> if (k == nlongs - 1) {
>> @@ -1294,6 +1301,16 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
>> endmask = ~0UL;
>> }
>>
>> + if (maxnode > MAX_NUMNODES && MAX_NUMNODES % BITS_PER_LONG != 0) {
>> + unsigned long valid_mask = endmask;
>> +
>> + valid_mask &= ~((1UL << (MAX_NUMNODES % BITS_PER_LONG)) - 1);
>
> I'm not sure if the combination with endmask works in this case:
>
> 0 BITS_PER_LONG 2xBITS_PER_LONG
> |____________|____________|
> | |
> MAX_NUMNODES maxnode
>
> endmask will contain bits between 0 and maxnode
In the case, BITS_TO_LONGS(maxnode) > BITS_TO_LONGS(MAX_NUMNODES), right?
And after checking BITS_PER_LONG to 2xBITS_PER_LONGi 1/4 ?endmask will set to
"~0UL". e.g. endmask will be 0xffff ffff ffff ffff if
unsigned long is 64bit.
Then the valid_mask will just contain bits MAX_NUMNODES to BITS_PER_LONG.
Thanks
Yisheng Xie
> but here we want to check bits between MAX_NUMNODES and BITS_PER_LONG
> and endmask should not be mixed up with that?
>
>
> Vlastimil
>
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next prev parent reply other threads:[~2017-10-31 11:03 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-27 10:14 [PATCH RFC v2 0/4] some fixes and clean up for mempolicy Yisheng Xie
2017-10-27 10:14 ` [PATCH RFC v2 1/4] mm/mempolicy: Fix get_nodes() mask miscalculation Yisheng Xie
2017-10-31 8:34 ` Vlastimil Babka
2017-11-01 9:37 ` Yisheng Xie
2017-10-27 10:14 ` [PATCH RFC v2 2/4] mm/mempolicy: remove redundant check in get_nodes Yisheng Xie
2017-10-31 8:55 ` Vlastimil Babka
2017-10-27 10:14 ` [PATCH RFC v2 3/4] mm/mempolicy: fix the check of nodemask from user Yisheng Xie
2017-10-31 9:30 ` Vlastimil Babka
2017-10-31 11:01 ` Yisheng Xie [this message]
2017-10-31 11:28 ` Vlastimil Babka
2017-10-27 10:14 ` [PATCH RFC v2 4/4] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages Yisheng Xie
2017-10-31 9:46 ` Vlastimil Babka
2017-11-06 1:31 ` Yisheng Xie
2017-11-06 7:39 ` Vlastimil Babka
2017-11-06 15:29 ` Christopher Lameter
2017-11-07 11:23 ` Yisheng Xie
2017-11-07 14:54 ` Christopher Lameter
2017-11-07 15:05 ` Vlastimil Babka
2017-11-07 15:55 ` Christopher Lameter
2017-11-08 1:38 ` Yisheng Xie
2017-11-08 15:02 ` Christopher Lameter
2017-11-09 10:54 ` Yisheng Xie
2017-11-09 15:46 ` Christopher Lameter
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