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

[Kefeng Wang]

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@xxxxxxxxxx>
> > 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@xxxxxxxxxx>
> > Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>
> Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
>
> ... 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))


> .