mm/memblock.c: fix NULL dereference error

Hi Andrew,

this patch is part of https://lkml.org/lkml/2016/7/26/347 and isn't merged in as you advised in another mail, i release this patch against linus's mainline for fixing relevant bugs completely, see test patch attached for verification details

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From 5a74cb46b7754a45428ff95f4653ad27025c3131 Mon Sep 17 00:00:00 2001

From: zijun_hu <[email protected]>
Date: Tue, 2 Aug 2016 12:35:28 +0800
Subject: [PATCH] mm/memblock.c: fix NULL dereference error

it causes NULL dereference error and failure to get type_a->regions[0] info if parameter type_b of __next_mem_range_rev() == NULL

the bugs are fixed by checking before dereferring and initializing idx_b to 0

the approach is tested by dumping all types of region via __memblock_dump_all() and __next_mem_range_rev() fixed to UART separately, the result is okay after checking the logs

Signed-off-by zijun_hu <[email protected]>

Tested-by zijun_hu <[email protected]>

Acked-by Tejun Heo <[email protected]>

---
 mm/memblock.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

mm/memblock.c +0 -0

index ff5ff3b..250dd48 100644
@@ -994,7 +994,10 @@ void __init_memblock __next_mem_range_rev(u64 *idx, int nid, ulong flags,
 

Hi zijun_hu,

[auto build test WARNING on mmotm/master]
[also build test WARNING on v4.7 next-20160801]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/zijun_hu/mm-memblock-c-fix-NULL-dereference-error/20160802-130708
base:   git://git.cmpxchg.org/linux-mmotm.git master
config: i386-randconfig-x009-201631 (attached as .config)
compiler: gcc-6 (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

In file included from include/linux/kernel.h:13:0,

                    from mm/memblock.c:13:

mm/memblock.c: In function 'memblock_patch_verify':

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mm/memblock.c:1713:11: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 3 has type 'phys_addr_t {aka unsigned int}' [-Wformat=]

      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
              ^
   include/linux/printk.h:260:21: note: in definition of macro 'pr_fmt'
    #define pr_fmt(fmt) fmt
                        ^~~

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mm/memblock.c:1713:3: note: in expansion of macro 'pr_info'

      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
      ^~~~~~~
   mm/memblock.c:1713:11: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 4 has type 'phys_addr_t {aka unsigned int}' [-Wformat=]
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
              ^
   include/linux/printk.h:260:21: note: in definition of macro 'pr_fmt'
    #define pr_fmt(fmt) fmt
                        ^~~

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mm/memblock.c:1713:3: note: in expansion of macro 'pr_info'

      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
      ^~~~~~~
   mm/memblock.c:1719:11: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 3 has type 'phys_addr_t {aka unsigned int}' [-Wformat=]
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
              ^
   include/linux/printk.h:260:21: note: in definition of macro 'pr_fmt'
    #define pr_fmt(fmt) fmt
                        ^~~
   mm/memblock.c:1719:3: note: in expansion of macro 'pr_info'
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
      ^~~~~~~
   mm/memblock.c:1719:11: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 4 has type 'phys_addr_t {aka unsigned int}' [-Wformat=]
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
              ^
   include/linux/printk.h:260:21: note: in definition of macro 'pr_fmt'
    #define pr_fmt(fmt) fmt
                        ^~~
   mm/memblock.c:1719:3: note: in expansion of macro 'pr_info'
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
      ^~~~~~~
   mm/memblock.c:1726:11: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 3 has type 'phys_addr_t {aka unsigned int}' [-Wformat=]
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
              ^
   include/linux/printk.h:260:21: note: in definition of macro 'pr_fmt'
    #define pr_fmt(fmt) fmt
                        ^~~
   mm/memblock.c:1726:3: note: in expansion of macro 'pr_info'
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
      ^~~~~~~
   mm/memblock.c:1726:11: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 4 has type 'phys_addr_t {aka unsigned int}' [-Wformat=]
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
              ^
   include/linux/printk.h:260:21: note: in definition of macro 'pr_fmt'
    #define pr_fmt(fmt) fmt
                        ^~~
   mm/memblock.c:1726:3: note: in expansion of macro 'pr_info'
      pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
      ^~~~~~~

vim +1713 mm/memblock.c

1697 pr_info(" memory size = %#llx reserved size = %#llx\n",
1698 (unsigned long long)memblock.memory.total_size,
1699 (unsigned long long)memblock.reserved.total_size);
1700
1701 memblock_dump(&memblock.memory, "memory");
1702 memblock_dump(&memblock.reserved, "reserved");
1703 }
1704
1705 void __init_memblock memblock_patch_verify(void)
1706 {
1707 u64 i;
1708 phys_addr_t this_start, this_end;
1709
1710 pr_info("in %s: memory\n", __func__);
1711 for_each_mem_range_rev(i, &memblock.memory, NULL, NUMA_NO_NODE,
1712 MEMBLOCK_NONE, &this_start, &this_end, NULL)

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1713 pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",

1714 i, this_start, this_end);
1715
1716 pr_info("in %s: reserved\n", __func__);
1717 for_each_mem_range_rev(i, &memblock.reserved, NULL, NUMA_NO_NODE,
1718 MEMBLOCK_NONE, &this_start, &this_end, NULL)
1719 pr_info("[%#016llx]\t[%#016llx-%#016llx]\n",
1720 i, this_start, this_end);
1721

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