Calling a kmalloc_node on a possible node which is not yet onlined can
lead to panic. Currently node_present_pages() doesn't verify the node is
online before accessing the pgdat for the node. However pgdat struct may
not be available resulting in a crash.

NIP [c0000000003d55f4] ___slab_alloc+0x1f4/0x760
LR [c0000000003d5b94] __slab_alloc+0x34/0x60
Call Trace:
[c0000008b3783960] [c0000000003d5734] ___slab_alloc+0x334/0x760 (unreliable)
[c0000008b3783a40] [c0000000003d5b94] __slab_alloc+0x34/0x60
[c0000008b3783a70] [c0000000003d6fa0] __kmalloc_node+0x110/0x490
[c0000008b3783af0] [c0000000003443d8] kvmalloc_node+0x58/0x110
[c0000008b3783b30] [c0000000003fee38] mem_cgroup_css_online+0x108/0x270
[c0000008b3783b90] [c000000000235aa8] online_css+0x48/0xd0
[c0000008b3783bc0] [c00000000023eaec] cgroup_apply_control_enable+0x2ec/0x4d0
[c0000008b3783ca0] [c000000000242318] cgroup_mkdir+0x228/0x5f0
[c0000008b3783d10] [c00000000051e170] kernfs_iop_mkdir+0x90/0xf0
[c0000008b3783d50] [c00000000043dc00] vfs_mkdir+0x110/0x230
[c0000008b3783da0] [c000000000441c90] do_mkdirat+0xb0/0x1a0
[c0000008b3783e20] [c00000000000b278] system_call+0x5c/0x68

Fix this by verifying the node is online before accessing the pgdat
structure. Fix the same for node_spanned_pages() too.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Sachin Sant <redacted>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Christopher Lameter <redacted>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Joonsoo Kim <redacted>
Cc: Kirill Tkhai <redacted>
Cc: Vlastimil Babka <redacted>
Cc: Srikar Dronamraju <redacted>
Cc: Bharata B Rao <redacted>

Reported-by: Sachin Sant <redacted>
Tested-by: Sachin Sant <redacted>
Signed-off-by: Srikar Dronamraju <redacted>
---
 include/linux/mmzone.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index f3f264826423..88078a3b95e5 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h

@@ -756,8 +756,10 @@ typedef struct pglist_data {
 	atomic_long_t		vm_stat[NR_VM_NODE_STAT_ITEMS];
 } pg_data_t;
 
-#define node_present_pages(nid)	(NODE_DATA(nid)->node_present_pages)
-#define node_spanned_pages(nid)	(NODE_DATA(nid)->node_spanned_pages)
+#define node_present_pages(nid)		\
+	(node_online(nid) ? NODE_DATA(nid)->node_present_pages : 0)
+#define node_spanned_pages(nid)		\
+	(node_online(nid) ? NODE_DATA(nid)->node_spanned_pages : 0)
 #ifdef CONFIG_FLAT_NODE_MEM_MAP
 #define pgdat_page_nr(pgdat, pagenr)	((pgdat)->node_mem_map + (pagenr))
 #else

-- 
2.18.1