From f0093ede9b726ccb1876d43574f5b45c79940aca Mon Sep 17 00:00:00 2001 From: Yasuaki Ishimatsu Date: Wed, 6 Aug 2014 16:07:03 -0700 Subject: [PATCH] drivers/firmware/memmap.c: don't allocate firmware_map_entry of same memory range 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: sysfs_open_file+0x46/0x2b0 PGD 203a89fe067 PUD 0 Oops: 0000 [#1] SMP ... Call Trace: do_dentry_open+0x1ef/0x2a0 finish_open+0x31/0x40 do_last+0x57c/0x1220 path_openat+0xc2/0x4c0 do_filp_open+0x4b/0xb0 do_sys_open+0xf3/0x1f0 SyS_open+0x1e/0x20 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 Cc: Santosh Shilimkar Cc: Toshi Kani Cc: Greg Kroah-Hartman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/firmware/memmap.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/firmware/memmap.c b/drivers/firmware/memmap.c index 1815849f83cb..79f18e6d9c4f 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); -- 2.20.1