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Subject[PATCH] hugetlb: fix uninitialized subpool pointer
Date
Gerald Schaefer reported a panic on s390 in hugepage_subpool_put_pages()
with linux-next 5.12.0-20210222.
Call trace:
hugepage_subpool_put_pages.part.0+0x2c/0x138
__free_huge_page+0xce/0x310
alloc_pool_huge_page+0x102/0x120
set_max_huge_pages+0x13e/0x350
hugetlb_sysctl_handler_common+0xd8/0x110
hugetlb_sysctl_handler+0x48/0x58
proc_sys_call_handler+0x138/0x238
new_sync_write+0x10e/0x198
vfs_write.part.0+0x12c/0x238
ksys_write+0x68/0xf8
do_syscall+0x82/0xd0
__do_syscall+0xb4/0xc8
system_call+0x72/0x98

This is a result of the change which moved the hugetlb page subpool
pointer from page->private to page[1]->private. When new pages are
allocated from the buddy allocator, the private field of the head
page will be cleared, but the private field of subpages is not modified.
Therefore, old values may remain.

Fix by initializing hugetlb page subpool pointer in prep_new_huge_page().

Fixes: f1280272ae4d ("hugetlb: use page.private for hugetlb specific page flags")
Reported-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
mm/hugetlb.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c232cb67dda2..7ae5c18c98a7 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1465,6 +1465,7 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
{
INIT_LIST_HEAD(&page->lru);
set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
+ hugetlb_set_page_subpool(page, NULL);
set_hugetlb_cgroup(page, NULL);
set_hugetlb_cgroup_rsvd(page, NULL);
spin_lock(&hugetlb_lock);
--
2.29.2
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