mm: page_alloc: fix CMA area initialisation when pageblock > MAX_ORDER

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:
    __list_add+0x10/0xd4
    free_one_page+0x26c/0x638
    __free_pages_ok.part.52+0x84/0xbc
    __free_pages+0x74/0xbc
    init_cma_reserved_pageblock+0xe8/0x104
    cma_init_reserved_areas+0x190/0x1e4
    do_one_initcall+0xc4/0x154
    kernel_init_freeable+0x204/0x2a8
    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
than 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
â\80\9cpageblock_order > MAX_ORDERâ\80\9d 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.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Reported-by: Mark Salter <msalter@redhat.com>
Tested-by: Mark Salter <msalter@redhat.com>
Tested-by: Christopher Covington <cov@codeaurora.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: <stable@vger.kernel.org>	[3.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 20d17f8266fed9e482055c5c68034b8149f3329c..0ea758b898fdae74dbe5bf414b8995c4c944e7b3 100644 (file)
--- 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