From e47608ab6dbe63fefe60c211a30b3fc78a1b5d5e Mon Sep 17 00:00:00 2001 From: zijun_hu Date: Thu, 4 Aug 2016 15:32:00 -0700 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 Fix this 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. Link: http://lkml.kernel.org/r/57A0320D.6070102@zoho.com Signed-off-by: zijun_hu Tested-by: zijun_hu Acked-by: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memblock.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/memblock.c b/mm/memblock.c index 1f065da87327..483197ef613f 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -994,7 +994,10 @@ void __init_memblock __next_mem_range_rev(u64 *idx, int nid, ulong flags, if (*idx == (u64)ULLONG_MAX) { idx_a = type_a->cnt - 1; - idx_b = type_b->cnt; + if (type_b != NULL) + idx_b = type_b->cnt; + else + idx_b = 0; } for (; idx_a >= 0; idx_a--) { -- 2.20.1