With a kernel configured with ARM64_64K_PAGES && !TRANSPARENT_HUGEPAGE,
the following is triggered at early boot:
SMP: Total of 8 processors activated.
devtmpfs: initialized
Unable to handle kernel NULL pointer dereference at virtual address 00000008
pgd = fffffe0000050000
[00000008] *pgd=00000043fba00003, *pmd=00000043fba00003, *pte=00e0000078010407
Internal error: Oops: 96000006 [#1] SMP
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.15.0-rc864k+ #44
task: fffffe03bc040000 ti: fffffe03bc080000 task.ti: fffffe03bc080000
PC is at __list_add+0x10/0xd4
LR is at free_one_page+0x270/0x638
...
Call trace:
[<fffffe00003ee970>] __list_add+0x10/0xd4
[<fffffe000019c478>] free_one_page+0x26c/0x638
[<fffffe000019c8c8>] __free_pages_ok.part.52+0x84/0xbc
[<fffffe000019d5e8>] __free_pages+0x74/0xbc
[<fffffe0000c01350>] init_cma_reserved_pageblock+0xe8/0x104
[<fffffe0000c24de0>] cma_init_reserved_areas+0x190/0x1e4
[<fffffe0000090418>] do_one_initcall+0xc4/0x154
[<fffffe0000bf0a50>] kernel_init_freeable+0x204/0x2a8
[<fffffe00007520a0>] kernel_init+0xc/0xd4
This happens because init_cma_reserved_pageblock() calls
__free_one_page() with pageblock_order as page order but it is bigger
han MAX_ORDER. This in turn causes accesses past zone->free_list[].
Fix the problem by changing init_cma_reserved_pageblock() such that it
splits pageblock into individual MAX_ORDER pages if pageblock is
bigger than a MAX_ORDER page.
In cases where !CONFIG_HUGETLB_PAGE_SIZE_VARIABLE, which is all
architectures expect for ia64, powerpc and tile at the moment, the
“pageblock_order > MAX_ORDER” condition will be optimised out since
both sides of the operator are constants. In cases where pageblock
size is variable, the performance degradation should not be
significant anyway since init_cma_reserved_pageblock() is called
only at boot time at most MAX_CMA_AREAS times which by default is
eight.
Cc: <stable@xxxxxxxxxxxxxxx> # v3.5+
Signed-off-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
Reported-and-tested-by: Mark Salter <msalter@xxxxxxxxxx>
Tested-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
---
mm/page_alloc.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
Resent with somehow bigger distribution including Andrew, Mel and
linux-mm, as well as stable.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ee92384..fef9614 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -816,9 +816,21 @@ void __init init_cma_reserved_pageblock(struct page *page)
set_page_count(p, 0);
} while (++p, --i);
- set_page_refcounted(page);
set_pageblock_migratetype(page, MIGRATE_CMA);
- __free_pages(page, pageblock_order);
+
+ if (pageblock_order >= MAX_ORDER) {
+ i = pageblock_nr_pages;
+ p = page;
+ do {
+ set_page_refcounted(p);
+ __free_pages(p, MAX_ORDER - 1);
+ p += MAX_ORDER_NR_PAGES;
+ } while (i -= MAX_ORDER_NR_PAGES);
+ } else {
+ set_page_refcounted(page);
+ __free_pages(page, pageblock_order);
+ }
+
adjust_managed_page_count(page, pageblock_nr_pages);
}
#endif
--
2.0.0.526.g5318336
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