[PATCH v4 3/3] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages

[PATCH v4 3/3] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages

[Yisheng Xie]

As in manpage of migrate_pages, the errno should be set to EINVAL when
none of the node IDs specified by new_nodes are on-line and allowed by the
process's current cpuset context, or none of the specified nodes contain
memory.  However, when test by following case:

	new_nodes = 0;
	old_nodes = 0xf;
	ret = migrate_pages(pid, old_nodes, new_nodes, MAX);

The ret will be 0 and no errno is set.  As the new_nodes is empty, we
should expect EINVAL as documented.

To fix the case like above, this patch check whether target nodes AND
current task_nodes is empty, and then check whether AND
node_states[N_MEMORY] is empty.

Meanwhile,this patch also remove the check of EPERM on CAP_SYS_NICE. 
The caller of migrate_pages should be able to migrate the target process
pages anywhere the caller can allocate memory, if the caller can access
the mm_struct.

Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Chris Salls <salls@cs.ucsb.edu>
Cc: Christopher Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Tan Xiaojun <tanxiaojun@huawei.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
---
v3:
 * check whether node is empty after AND current task node, and then nodes
   which have memory
v4:
 * remove the check of EPERM on CAP_SYS_NICE.

Hi Vlastimil and Christopher,

Could you please help to review this version?

Thanks
Yisheng Xie

 mm/mempolicy.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 65df28d..4da74b6 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1426,17 +1426,14 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode,
 	}
 	rcu_read_unlock();
 
-	task_nodes = cpuset_mems_allowed(task);
-	/* Is the user allowed to access the target nodes? */
-	if (!nodes_subset(*new, task_nodes) && !capable(CAP_SYS_NICE)) {
-		err = -EPERM;
+	task_nodes = cpuset_mems_allowed(current);
+	nodes_and(*new, *new, task_nodes);
+	if (nodes_empty(*new))
 		goto out_put;
-	}
 
-	if (!nodes_subset(*new, node_states[N_MEMORY])) {
-		err = -EINVAL;
+	nodes_and(*new, *new, node_states[N_MEMORY]);
+	if (nodes_empty(*new))
 		goto out_put;
-	}
 
 	err = security_task_movememory(task);
 	if (err)
-- 
1.7.12.4

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH v4 3/3] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages

[Vlastimil Babka]

On 12/01/2017 10:55 AM, Yisheng Xie wrote:
> As in manpage of migrate_pages, the errno should be set to EINVAL when
> none of the node IDs specified by new_nodes are on-line and allowed by the
> process's current cpuset context, or none of the specified nodes contain
> memory.  However, when test by following case:
> 
> 	new_nodes = 0;
> 	old_nodes = 0xf;
> 	ret = migrate_pages(pid, old_nodes, new_nodes, MAX);
> 
> The ret will be 0 and no errno is set.  As the new_nodes is empty, we
> should expect EINVAL as documented.
> 
> To fix the case like above, this patch check whether target nodes AND
> current task_nodes is empty, and then check whether AND
> node_states[N_MEMORY] is empty.
> 
> Meanwhile,this patch also remove the check of EPERM on CAP_SYS_NICE. 
> The caller of migrate_pages should be able to migrate the target process
> pages anywhere the caller can allocate memory, if the caller can access
> the mm_struct.
> 
> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Chris Salls <salls@cs.ucsb.edu>
> Cc: Christopher Lameter <cl@linux.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Tan Xiaojun <tanxiaojun@huawei.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> ---
> v3:
>  * check whether node is empty after AND current task node, and then nodes
>    which have memory
> v4:
>  * remove the check of EPERM on CAP_SYS_NICE.
> 
> Hi Vlastimil and Christopher,
> 
> Could you please help to review this version?

Hi, I think we should stay with v3 after all. What I missed when
reviewing it, is that the EPERM check is for cpuset_mems_allowed(task)
and in v3 you add EINVAL check for cpuset_mems_allowed(current), which
may not be the same, and the intention of CAP_SYS_NICE is not whether we
can bypass our own cpuset, but whether we can bypass the target task's
cpuset. Sorry for the confusion.

> Thanks
> Yisheng Xie
> 
>  mm/mempolicy.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 65df28d..4da74b6 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1426,17 +1426,14 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode,
>  	}
>  	rcu_read_unlock();
>  
> -	task_nodes = cpuset_mems_allowed(task);
> -	/* Is the user allowed to access the target nodes? */
> -	if (!nodes_subset(*new, task_nodes) && !capable(CAP_SYS_NICE)) {
> -		err = -EPERM;
> +	task_nodes = cpuset_mems_allowed(current);
> +	nodes_and(*new, *new, task_nodes);
> +	if (nodes_empty(*new))
>  		goto out_put;
> -	}
>  
> -	if (!nodes_subset(*new, node_states[N_MEMORY])) {
> -		err = -EINVAL;
> +	nodes_and(*new, *new, node_states[N_MEMORY]);
> +	if (nodes_empty(*new))
>  		goto out_put;
> -	}
>  
>  	err = security_task_movememory(task);
>  	if (err)
> 

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH v4 3/3] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages

[Yisheng Xie]

Hi Vlastimil,

On 2017/12/1 23:18, Vlastimil Babka wrote:
> On 12/01/2017 10:55 AM, Yisheng Xie wrote:
>> As in manpage of migrate_pages, the errno should be set to EINVAL when
>> none of the node IDs specified by new_nodes are on-line and allowed by the
>> process's current cpuset context, or none of the specified nodes contain
>> memory.  However, when test by following case:
>>
>> 	new_nodes = 0;
>> 	old_nodes = 0xf;
>> 	ret = migrate_pages(pid, old_nodes, new_nodes, MAX);
>>
>> The ret will be 0 and no errno is set.  As the new_nodes is empty, we
>> should expect EINVAL as documented.
>>
>> To fix the case like above, this patch check whether target nodes AND
>> current task_nodes is empty, and then check whether AND
>> node_states[N_MEMORY] is empty.
>>
>> Meanwhile,this patch also remove the check of EPERM on CAP_SYS_NICE. 
>> The caller of migrate_pages should be able to migrate the target process
>> pages anywhere the caller can allocate memory, if the caller can access
>> the mm_struct.
>>
>> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
>> Cc: Andi Kleen <ak@linux.intel.com>
>> Cc: Chris Salls <salls@cs.ucsb.edu>
>> Cc: Christopher Lameter <cl@linux.com>
>> Cc: David Rientjes <rientjes@google.com>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
>> Cc: Tan Xiaojun <tanxiaojun@huawei.com>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> ---
>> v3:
>>  * check whether node is empty after AND current task node, and then nodes
>>    which have memory
>> v4:
>>  * remove the check of EPERM on CAP_SYS_NICE.
>>
>> Hi Vlastimil and Christopher,
>>
>> Could you please help to review this version?
> 
> Hi, I think we should stay with v3 after all. What I missed when
> reviewing it, is that the EPERM check is for cpuset_mems_allowed(task)
> and in v3 you add EINVAL check for cpuset_mems_allowed(current), which
> may not be the same, and the intention of CAP_SYS_NICE is not whether we
> can bypass our own cpuset, but whether we can bypass the target task's
> cpuset. Sorry for the confusion.

Ok, so please ignore this version.

Thanks
Yisheng Xie
> 
> 
> .
> 

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>