From f2f36b8acbd0d5b9a5daa57b9b1ff7603f08a917 Mon Sep 17 00:00:00 2001
From: Jialong Chen <chenjialong@huawei.com>
Date: Sat, 13 Jul 2019 17:36:29 +0800
Subject: [PATCH] crash: fix bitmap_len calculation overflow problem in large memory
 address
reason: variable overflow causes a logic error in crash.
crash: page excluded: kernel virtual address: ffff0000089c9100  type: "kernel_config_data"
WARNING: cannot read kernel_config_data
crash: page excluded: kernel virtual address: ffff00000911b938  type: "possible"
WARNING: cannot read cpu_possible_map
crash: page excluded: kernel virtual address: ffff00000911b8b8  type: "present"
WARNING: cannot read cpu_present_map
crash: page excluded: kernel virtual address: ffff00000911b838  type: "online"
WARNING: cannot read cpu_online_map
crash: page excluded: kernel virtual address: ffff00000911b9b8  type: "active"
WARNING: cannot read cpu_active_map
crash: page excluded: kernel virtual address: ffff0000093ec9d0  type: "shadow_timekeeper xtime_sec"
crash: page excluded: kernel virtual address: ffff000009124d2c  type: "init_uts_ns"
crash: vmlinux and vmcore do not match!
------------------------------------------------------------
602770ecf000-6027ffffffff : System RAM
------------------------------------------------------------
1)
int block_size=(int)sysconf(_SC_PAGESIZE);
off_t bitmap_len;
...
bitmap_len = block_size * header->bitmap_blocks;
bitmap_len overflow.
2)
static inline int 
get_bit(char *map, int byte, int bit)
{
	return map[byte] & (1<<bit);
}

static inline int 
page_is_ram(unsigned long nr)
{
	return get_bit(dd->bitmap, nr >> 3, nr & 7);
}
current nr=0x6027fff4f,
byte overflow when call get_bit.


Signed-off-by: Jialong Chen <chenjialong@huawei.com>
---
 diskdump.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/diskdump.c b/diskdump.c
index c3e343b..1a2a5ce 100644
--- a/diskdump.c
+++ b/diskdump.c
@@ -233,7 +233,7 @@ clean_diskdump_data(void)
 }
 
 static inline int 
-get_bit(char *map, int byte, int bit)
+get_bit(char *map, unsigned long byte, int bit)
 {
 	return map[byte] & (1<<bit);
 }
@@ -674,7 +674,7 @@ restart:
 		dd->max_mapnr = header->max_mapnr;
 
 	/* read memory bitmap */
-	bitmap_len = block_size * header->bitmap_blocks;
+	bitmap_len = (off_t)block_size * header->bitmap_blocks;
 	dd->bitmap_len = bitmap_len;
 
 	offset = (off_t)block_size * (1 + header->sub_hdr_size);
-- 
2.19.1