Re: [PATCH v3 1/4] hugetlb: Fix wrong use of nr_online_nodes

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2022/4/15 10:09, Davidlohr Bueso wrote:
> On Wed, 13 Apr 2022, Peng Liu wrote:
>
>> Certain systems are designed to have sparse/discontiguous nodes. In
>> this case, nr_online_nodes can not be used to walk through numa node.
>> Also, a valid node may be greater than nr_online_nodes.
>>
>> However, in hugetlb, it is assumed that nodes are contiguous. Recheck
>> all the places that use nr_online_nodes, and repair them one by one.
>>
>> Suggested-by: David Hildenbrand <david@redhat.com>
>> Fixes: 4178158ef8ca ("hugetlbfs: fix issue of preallocation of 
>> gigantic pages can't work")
>> Fixes: b5389086ad7b ("hugetlbfs: extend the definition of hugepages 
>> parameter to support node allocation")
>> Fixes: e79ce9832316 ("hugetlbfs: fix a truncation issue in hugepages 
>> parameter")
>> Fixes: f9317f77a6e0 ("hugetlb: clean up potential spectre issue 
>> warnings")
>> Signed-off-by: Peng Liu <liupeng256@huawei.com>
>> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
>
> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
>
> ... but
>
>> ---
>> mm/hugetlb.c | 12 ++++++------
>> 1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index b34f50156f7e..5b5a2a5a742f 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -2979,7 +2979,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, 
>> int nid)
>>     struct huge_bootmem_page *m = NULL; /* initialize for clang */
>>     int nr_nodes, node;
>>
>> -    if (nid != NUMA_NO_NODE && nid >= nr_online_nodes)
>> +    if (nid != NUMA_NO_NODE && !node_online(nid))
>
> afaict null_blk could also use this, actually the whole thing wants a
> helper - node_valid()?
>
This one should be unnecessary, and this patch looks has a bug,

if a very nid passed to node_online(), it may crash,  could you re-check 
it,

see my changes below,

1) add tmp check against MAX_NUMNODES before node_online() check,

     and move it after get tmp in hugepages_setup() , this could cover 
both per-node alloc and normal alloc

2) due to for_each_online_node() usage, we can drop additional check of 
nid in __alloc_bootmem_huge_page()


$ git diff
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index fb5a549169ce..5a3ddec181a0 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2986,8 +2986,6 @@ int __alloc_bootmem_huge_page(struct hstate *h, 
int nid)
         struct huge_bootmem_page *m = NULL; /* initialize for clang */
         int nr_nodes, node;

-       if (nid != NUMA_NO_NODE && nid >= nr_online_nodes)
-               return 0;
         /* do node specific alloc */
         if (nid != NUMA_NO_NODE) {
                 m = memblock_alloc_try_nid_raw(huge_page_size(h), 
huge_page_size(h),
@@ -3095,7 +3093,7 @@ static void __init 
hugetlb_hstate_alloc_pages(struct hstate *h)
         }

         /* do node specific alloc */
-       for (i = 0; i < nr_online_nodes; i++) {
+       for_each_online_node(i) {
                 if (h->max_huge_pages_node[i] > 0) {
                         hugetlb_hstate_alloc_pages_onenode(h, i);
                         node_specific_alloc = true;
@@ -4059,7 +4057,7 @@ static int __init hugetlb_init(void)
                         default_hstate.max_huge_pages =
                                 default_hstate_max_huge_pages;

-                       for (i = 0; i < nr_online_nodes; i++)
+                       for_each_online_node(i)
default_hstate.max_huge_pages_node[i] =
default_hugepages_in_node[i];
                 }
@@ -4168,15 +4166,15 @@ static int __init hugepages_setup(char *s)
                 count = 0;
                 if (sscanf(p, "%lu%n", &tmp, &count) != 1)
                         goto invalid;
+               if (tmp > MAX_NUMNODES || !node_online(tmp))
+                       goto invalid;
                 /* Parameter is node format */
                 if (p[count] == ':') {
                         if (!hugetlb_node_alloc_supported()) {
                                 pr_warn("HugeTLB: architecture can't 
support node specific alloc, ignoring!\n");
                                 return 0;
                         }
-                       if (tmp >= nr_online_nodes)
-                               goto invalid;
-                       node = array_index_nospec(tmp, nr_online_nodes);
+                       node = array_index_nospec(tmp, MAX_NUMNODES);
                         p += count + 1;
                         /* Parse hugepages */
                         if (sscanf(p, "%lu%n", &tmp, &count) != 1)
@@ -4304,7 +4302,7 @@ static int __init default_hugepagesz_setup(char *s)
          */
         if (default_hstate_max_huge_pages) {
                 default_hstate.max_huge_pages = 
default_hstate_max_huge_pages;
-               for (i = 0; i < nr_online_nodes; i++)
+               for_each_online_node(i)
                         default_hstate.max_huge_pages_node[i] =
                                 default_hugepages_in_node[i];
                 if (hstate_is_gigantic(&default_hstate))


> .