When limiting memory by mem= and ACPI DSDT table has PNP0C80,
firmware_map_entrys of same memory range are allocated and
memmap X sysfses which have same memory range are created as
follows:
# cat /sys/firmware/memmap/0/*
0x407ffffffff
0x40000000000
System RAM
# cat /sys/firmware/memmap/33/*
0x407ffffffff
0x40000000000
System RAM
# cat /sys/firmware/memmap/35/*
0x407ffffffff
0x40000000000
System RAM
In this case, when hot-removing memory, kernel panic occurs, showing
following call trace:
BUG: unable to handle kernel paging request at 00000001003e000b
IP: [<ffffffff81225c26>] sysfs_open_file+0x46/0x2b0
PGD 203a89fe067 PUD 0
Oops: 0000 [#1] SMP
...
Call Trace:
[<ffffffff811ad95f>] do_dentry_open+0x1ef/0x2a0
[<ffffffff811bba32>] ? __inode_permission+0x52/0xc0
[<ffffffff81225be0>] ? sysfs_schedule_callback+0x1c0/0x1c0
[<ffffffff811ada41>] finish_open+0x31/0x40
[<ffffffff811bf6ac>] do_last+0x57c/0x1220
[<ffffffff8119529e>] ? kmem_cache_alloc_trace+0x1ce/0x1f0
[<ffffffff811c0412>] path_openat+0xc2/0x4c0
[<ffffffff81167e2c>] ? tlb_flush_mmu.part.53+0x4c/0x90
[<ffffffff811c102b>] do_filp_open+0x4b/0xb0
[<ffffffff811cd827>] ? __alloc_fd+0xa7/0x130
[<ffffffff811aeed3>] do_sys_open+0xf3/0x1f0
[<ffffffff811aefee>] SyS_open+0x1e/0x20
[<ffffffff815f2199>] system_call_fastpath+0x16/0x1b
The problem occurs as follows:
When calling e820_reserve_resources(), firmware_map_entrys of all
e820 memory map are allocated. And all firmware_map_entrys is added
map_entries list as follows:
map_entries
-> +--- entry A --------+ -> ...
| start 0x407ffffffff|
| end 0x40000000000|
| type System RAM |
+--------------------+
After that, if ACPI DSDT table has PNP0C80 and the memory range is
limited by mem=, the PNP0C80 is hot-added. Then firmware_map_entry of
PNP0C80 is allocated and added map_entries list as follows:
map_entries
-> +--- entry A --------+ -> ... -> +--- entry B --------+
| start 0x407ffffffff| | start 0x407ffffffff|
| end 0x40000000000| | end 0x40000000000|
| type System RAM | | type System RAM |
+--------------------+ +--------------------+
Then memmap 0 sysfs for entry B is created.
After that, firmware_memmap_init() creates memmap sysfses of all
firmware_map_entrys in map_entries list. As a result, memmap 33
sysfs for entry A and memmap 35 sysfs for entry B are created.
But kobject of entry B has been used by memmap 0 sysfs. So
when creating memmap 35 sysfs, the kobject is broken.
If hot-removing memory, memmap 0 sysfs is destroyed and kobject of
memmap 0 sysfs is freed. But the kobject can be accessed via
memmap 35 sysfs. So when open memmap 35 sysfs, kernel panic occurs.
This patch checks whether there is firmware_map_entry of same memory
range in map_entries list and don't allocate firmware_map_entry of
same memroy range.
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
---
drivers/firmware/memmap.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/firmware/memmap.c b/drivers/firmware/memmap.c
index 1815849..79f18e6 100644
--- a/drivers/firmware/memmap.c
+++ b/drivers/firmware/memmap.c
@@ -286,6 +286,10 @@ int __meminit firmware_map_add_hotplug(u64 start, u64 end, const char *type)
{
struct firmware_map_entry *entry;
+ entry = firmware_map_find_entry(start, end - 1, type);
+ if (entry)
+ return 0;
+
entry = firmware_map_find_entry_bootmem(start, end - 1, type);
if (!entry) {
entry = kzalloc(sizeof(struct firmware_map_entry), GFP_ATOMIC);
--
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